Leetcode算法题-解法转载-优快云博客

本文链接：https://blog.youkuaiyun.com/binbigdata/article/details/86601716

版权声明：本文为博主原创文章，未经博主允许不得转载。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/85112591
作者：负雪明烛
id：   fuxuemingzhu
个人博客：   http://fuxuemingzhu.cn/

把自己刷过的所有题目做一个整理，并且用简洁的语言概括了一下思路，汇总成了一个表格。

题目的排列顺序是按照先Easy再Medium再Hard排列的，暂时还没有把题目全部整理完成。后序我会把刷过的所有的题目都整理到这个文档里。

题目   难度   解法   题目地址
566. Reshape the Matrix   Easy   变长数组，求余法，维护行列计算在新的数组中的位置   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83626519
897. Increasing Order Search Tree   Easy   直接中序遍历的结果放到链表结尾   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82349263
771. Jewels and Stones   Easy   字典统计次数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79188903
929. Unique Email Addresses   Easy   字符串+set统计个数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83478570
709. To Lower Case   Easy   ASIIC码操作ord,chr   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81015228
804. Unique Morse Code Words   Easy   字典映射 + set统计个数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79774003
905. Sort Array By Parity   Easy   自定义sorted函数的cmp为数字mod 2   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82732066
461. Hamming Distance   Easy   先异或再数1的个数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54138423
657. Robot Return to Origin   Easy   Counter统计，判断是否相等   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83663650
832. Flipping an Image   Easy   直接计算新的数组的每个位置的值即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80471495
617. Merge Two Binary Trees   Easy   树的递归操作   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79052953
28. Implement strStr()   Easy   字符串遍历+切片是否相等的判断   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79254558
890. Find and Replace Pattern   Easy   直接使用字典做映射   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82014687
814. Binary Tree Pruning   Medium   二叉树的后序遍历   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79858752
561. Array Partition I   Easy   排序+求和   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71412574
728. Self Dividing Numbers   Easy   直接遍历区间的每个数字进行判断   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79053113
852. Peak Index in a Mountain Array   Easy   二分查找的变种，使用Mid位置和左右位置比较   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80721162
922. Sort Array By Parity II   Easy   分别求出奇偶数组然后拼接   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83045735
883. Projection Area of 3D Shapes   Easy   分别计算三视图的面积即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81748335
908. Smallest Range I   Easy   直接数学计算   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82824685
867. Transpose Matrix   Easy   先构建数组再遍历实现翻转   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81015450
589. N-ary Tree Preorder Traversal   Easy   多叉树的先序遍历，可以用递归和迭代   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81021950
590. N-ary Tree Postorder Traversal   Easy   多叉树的后序遍历   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81017965
350. Intersection of Two Arrays II   Easy   先排序然后用两个指针移动找出数组交集   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54341965
876. Middle of the Linked List   Easy   快慢指针同时向链表后面移动   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81748484
700. Search in a Binary Search Tree   Easy   BST中节点的查找，递归   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81015754
933. Number of Recent Calls   Easy   找出满足一定条件的区间长度，可以使用二分或者队列   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83714891
559. Maximum Depth of N-ary Tree   Easy   求树的高度，可以使用BFS和DFS   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81021864
557. Reverse Words in a String III   Easy   字符串的单词分别翻转再拼接到一起就好了   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70141268
806. Number of Lines To Write String   Easy   使用字典保存每个字符的长度，然后统计每行的长度是否超过100就好了   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79810381
344. Reverse String   Easy   字符串翻转，[::-1   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51284382
811. Subdomain Visit Count   Easy   字典保存每个子域名出现的次数即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79789925
476. Number Complement   Easy   求数字的补数，方法是异或上与其二进制数字的长度相等的全1二进制数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54562124
821. Shortest Distance to a Character   Easy   过两遍数组，分别找出距离左边和右边的这个字符的最短距离   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80471765
500. Keyboard Row   Easy   使用字典保存每行元素，然后看每个单词是不是只由一行元素组成   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/68953517
893. Groups of Special-Equivalent Strings   Easy   把奇偶位置都取出来，重新拼接成字符串作为指纹，看总的有多少种指纹   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82083609
872. Leaf-Similar Trees   Easy   先序、中序、后序都能得到叶子序列   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81748617
884. Uncommon Words from Two Sentences   Easy   使用字典统计每个单词出现的次数，然后看字典keys()的交集，然后在字典中看是不是只出现了一次   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81749170
766. Toeplitz Matrix   Easy   判断每个斜线是否相等，方法是判断每个元素是否和其左上角元素相等   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79127213
463. Island Perimeter   Easy   求小岛的周长。使用所有陆地个数×4-相交部分×2.   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83868905
682. Baseball Game   Easy   用一个栈进行模拟   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79183412
868. Binary Gap   Easy   二进制表示中1的最大间距，保留上一个1的位置即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81079495
104. Maximum Depth of Binary Tree   Easy   二叉树的高度，可以用DFS和BFS   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/48490829
136. Single Number   Easy   所有的数字出现了两次，其中一个只出现了一次。找出这个数字的方法可以使用字典统计或者异或运算   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54173334
496. Next Greater Element I   Easy   找出某个数字右边比他大的数字，直接遍历查找就好了   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79080337
637. Average of Levels in Binary Tree   Easy   求每层的二叉树的均值，可以使用BFS和DFS   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79088554
693. Binary Number with Alternating Bits   Easy   判断数字的二进制表示是不是01交错的。直接遍历判断，或者位运算。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79089937
762. Prime Number of Set Bits in Binary Representation   Easy   判断二进制数字的1的个数是不是质数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79089092
917. Reverse Only Letters   Easy   只翻转字母其余字符不动，可以使用栈、双指针   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82956271
292. Nim Game   Easy   判断输入数字是不是4的倍数即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51284421
824. Goat Latin   Easy   字符串处理，简单   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80471925
892. Surface Area of 3D Shapes   Easy   统计立方体个数，减去相交面积   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82083893
784. Letter Case Permutation   Easy   经典回溯法，把字符的大小写分别拼接到字符串尾部   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79360330
258. Add Digits   Easy   两重循环，一直对每位数字求和直到剩余个位数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/49161129
283. Move Zeroes   Easy   使用一个指针指向第一个为0的位置，然后遍历不是0的位置进行交换   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51284981
748. Shortest Completing Word   Easy   找出符合某个模式的字符串，直接处理就好了   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79432228
690. Employee Importance   Easy   dfs   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79091343
389. Find the Difference   Easy   找多出来的字符，可以使用字典，也可以使用异或   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54174443
520. Detect Capital   Easy   统计大写字符的个数，判断是不是在首位   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/68957658
448. Find All Numbers Disappeared in an Array   Easy   用set去重，找出没有出现的数字即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/53981307
696. Count Binary Substrings   Easy   先找出连续的0，1个数，然后进行交错求最小值，在求和   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79183556
454. 4Sum II   Easy   4sum，先确定两个数字，然后看剩余两个数字的和是否出现过   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79473739
788. Rotated Digits   Easy   字典保存翻转后的数字，判断是否相等即可。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79378135
653. Two Sum IV - Input is a BST   Easy   BFS或者DFS，在遍历的过程中进行破案吨   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79120732
371. Sum of Two Integers   Easy   位运算   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79379939
349. Intersection of Two Arrays   Easy   用两个set求交集，然后转成List即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54236183
606. Construct String from Binary Tree   Easy   先序遍历，可以省略右子树，所以需要做一个节点是否存在的判断   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79121550
206. Reverse Linked List   Easy   翻转单链表，可以使用递归和迭代   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51290121
169. Majority Element   Easy   Moore投票法，或者字典统计次数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51288749
171. Excel Sheet Column Number   Easy   26进制，没有难度   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51286467
13. Roman to Integer   Easy   使用字典保存映射，遍历求值就好了。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/48208995
937. Reorder Log Files   Easy   分割排序，再拼接   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83961188
121. Best Time to Buy and Sell Stock   Easy   一次遍历，如果后一天比前一天大就买了卖   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51291151
242. Valid Anagram   Easy   判断字符串是否是同构的，直接统计词频或者排序   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51286195
860. Lemonade Change   Easy   贪心算法，找零钱先找大的面额，如果不够再用小的面额   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80913955
217. Contains Duplicate   Easy   判断数组是否有重复，可以统计词频，判断set长度是否相等，排序等方法   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51289768
427. Construct Quad Tree   Easy   建立四叉树，使用递归，判断4个叶子全部是0或者1   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81836838
706. Design HashMap   Easy   设计一个字典，直接开个很大的数组即可，内存放得下   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81017297
538. Convert BST to Greater Tree   Easy   把每个节点变成比它大的节点的值的和，采用逆中序遍历。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79132336
100. Same Tree   Easy   判断两棵数是否相等，直接递归   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51285076
530. Minimum Absolute Difference in BST   Easy   中序遍历，保存前一个节点，当前节点的值减去前一个节点的值   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/69666671
783. Minimum Distance Between BST Nodes   Easy   和上题完全一样   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79402127
383. Ransom Note   Easy   使用字典统计每个字符出现的次数，前者小于后者即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54178342
796. Rotate String   Easy   字符串切片   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79521194
717. 1-bit and 2-bit Characters   Easy   单次遍历，判断前面满足的条件下，最后一位是0即可。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79130681
453. Minimum Moves to Equal Array Elements   Easy   把n-1个数字加1，相等于把最大值-1.求和-n*最小值   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54177981
733. Flood Fill   Easy   对相同颜色进行染色，可以使用DFS和BFS.   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79401716
404. Sum of Left Leaves   Easy   求所有左叶子的和，要判断是不是在左边，判断是不是叶子，然后加到结果中   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54178595
447. Number of Boomerangs   Easy   统计回旋镖的个数，不能暴力解决，需要使用排列组合公式n*(n-1)   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54379349
598. Range Addition II   Easy   求队列的最小值即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79398272
492. Construct the Rectangle   Easy   从算术平方根开始找约数即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/68957959
167. Two Sum II - Input array is sorted   Easy   前后指针同时向中间走，找到target之后停止   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70232518
387. First Unique Character in a String   Easy   首先做个字符出现次数的统计，然后再次遍历，找出只出现了一次的第一个字符。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/84139374
697. Degree of an Array   Easy   求最大的出现次数的所有数字，其最左右出现的位置差的最小值   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79146067
455. Assign Cookies   Easy   贪心算法，尽可能给小孩满足其欲望的饼干   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54177627
108. Convert Sorted Array to Binary Search Tree   Easy   构建BST，使用中间数进行分割，用递归   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70665213
506. Relative Ranks   Easy   相对排名，可以使用堆或者排序或者argsort   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70173434
661. Image Smoother   Easy   直接暴力求平均即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79156499
409. Longest Palindrome   Easy   统计出现次数的奇偶就可以   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54236594
599. Minimum Index Sum of Two Lists   Easy   保存出现的索引和与元素的对应，使用堆保存最小的就行   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79138621
268. Missing Number   Easy   理论和-当前和   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70332471
563. Binary Tree Tilt   Easy   后序遍历函数返回的是左右子树的差，在里面用变量求和   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71440281
830. Positions of Large Groups   Easy   找到长度大于3的连续字符，需要判断结束！！   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80472242
350. Intersection of Two Arrays II   Easy   可以排序，也可以使用字典统计次数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54341965
543. Diameter of Binary Tree   Easy   递归求树的深度，同时求左右两个深度的和的最大值   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70338312
551. Student Attendance Record I   Easy   统计A的个数，并且判断连续L的个数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70337973
121. Best Time to Buy and Sell Stock   Easy   保存当前的最小值以及最大收益即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51291151
628. Maximum Product of Three Numbers   Easy   找出三个数最大的乘积   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79169635
401. Binary Watch   Easy   使用combinations函数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54344098
746. Min Cost Climbing Stairs   Easy   动态规划   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79188612
925. Long Pressed Name   Easy   使用双指针，统计连续字符出现的次数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83245395
541. Reverse String II   Easy   Python的切片翻转   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70141909
705. Design HashSet   Easy   直接开数组就行   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81016992
107. Binary Tree Level Order Traversal II   Easy   DFS和BFS都可以   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/49108449
504. Base 7   Easy   转成7进制   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70194688
115. Distinct Subsequences   Easy   动规，判断当前字符是否相等   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/84228383
21. Merge Two Sorted Lists   Easy   可以使用递归或者迭代   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51291406
458. Poor Pigs   Easy   类似拨号键盘，多维空间求解   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81079261
257. Binary Tree Paths   Easy   打印二叉树的路径，使用递归和迭代   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71249429
844. Backspace String Compare   Easy   字符串可以退格，使用栈轻松解决   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80643408
202. Happy Number   Easy   递归和迭代两种做法   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/49180507
674. Longest Continuous Increasing Subsequence   Easy   简单的动态规划   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79220527
744. Find Smallest Letter Greater Than Target   Easy   线性扫描或者二分   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79137225
118. Pascal’s Triangle   Easy   提前构造出来，然后处理每行即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51346488
671. Second Minimum Node In a Binary Tree   Easy   递归的时候找第二小值   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79222455
720. Longest Word in Dictionary   Easy   先排序，再找前缀是否存在。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79123277
27. Remove Element   Easy   使用双指针或者标记指针使得前面都是满足要求的，后面都不满足   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51303161
70. Climbing Stairs   Easy   动态规划   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51290778
415. Add Strings   Easy   直接模拟大整数加法，需要注意进位问题   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54380737
235. Lowest Common Ancestor of a Binary Search Tree   Easy   BST找公共祖先，使用递归很简单   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51290289
594. Longest Harmonious Subsequence   Easy   统计相邻的数字是否都存在即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79233752
101. Symmetric Tree   Easy   可以使用BFS和DFS两种方法   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51345707
53. Maximum Subarray   Easy   动态规划找子数组最大和   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71101802
819. Most Common Word   Easy   正则+统计   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80472079
231. Power of Two   Easy   判断二进制是不是只有1个1即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51290981
405. Convert a Number to Hexadecimal   Easy   转成16进制，难点在于负数的处理：加上1<<32   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54426643
83. Remove Duplicates from Sorted List   Easy   递归和循环   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51290506
326. Power of Three   Easy   循环和迭代   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51290895
191. Number of 1 Bits   Easy   使用位移统计二进制个数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51290376
437. Path Sum III   Easy   找路径的个数，使用DFS*2或者BFS+DFS   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71097135
704. Binary Search   Easy   二分的模板   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81017415
119. Pascal’s Triangle II   Easy   原地翻转可以用倒序遍历   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51348629
232. Implement Queue using Stacks   Easy   两个栈实现一个队列   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51345762
572. Subtree of Another Tree   Easy   DFS*2或DFS+BSF   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71440802
198. House Robber   Easy   简单dp，当前房间偷和不偷两种状态   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51291936
703. Kth Largest Element in a Stream   Easy   使用小根堆维护k个值，则第一个元素就是第k大元素   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81027116
345. Reverse Vowels of a String   Easy   使用栈进行翻转，或者使用双指针   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51291677
66. Plus One   Easy   使用carry表示进位   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51346096
263. Ugly Number   Easy   除去2,3,5因子即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/49183961
35. Search Insert Position   Easy   二分查找   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70738108
645. Set Mismatch   Easy   使用统计次数或者直接求和计算   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79247916
747. Largest Number At Least Twice of Others   Easy   找出最大值，然后弹掉，再找次大值即可。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79188909
342. Power of Four   Easy   递归和迭代   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51291091
724. Find Pivot Index   Easy   先求和，在遍历求前半部分的和，找出左边等于右边   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79248308
9. Palindrome Number   Easy   可以先翻转成整数，然后判断和原来的是否相等   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71334663
482. License Key Formatting   Easy   计算第一个分割的长度，后面都是等长的了   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79234075
1. Two Sum   Easy   保存已经出现过的数字的索引，当下次遍历的时候遇到了满足要求的结果，那么既是停止   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/72465759
459. Repeated Substring Pattern   Easy   判断每个子串重复多次能不能组成原来的串即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/54564801
849. Maximize Distance to Closest Person   Easy   从前向后以及从后向前遍历两次，取最近距离   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80643250
38. Count and Say   Easy   统计字符连续出现的次数，并说出来，需要注意最后的一个字符也要添加上去   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71618640
80. Remove Duplicates from Sorted Array II   Easy   快指针移动判断和慢指针是否相等，如果不等就换到前面来   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82829709
643. Maximum Average Subarray I   Easy   一定注意是长度为k的滑动窗口，注意下标   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79248629
501. Find Mode in Binary Search Tree   Easy   如果使用附加空间，可以使用字典保存次数；否则需要遍历两次，判断出现次数。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71124600
374. Guess Number Higher or Lower   Easy   使用二分查找   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71516105
743. Network Delay Time   Easy   dijkstra算法   https://leetcode.com/problems/network-delay-time/description/
558. Quad Tree Intersection   Easy   递归构造   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82356008
172. Factorial Trailing Zeroes   Easy   数有多少个5就行了   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51347044
441. Arranging Coins   Easy   二分查找满足条件的层数即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71330733
225. Implement Stack using Queues   Easy   使用一个队列就能实现栈，每次Push的时候，把队列里的所有元素弹出再放进来就好了。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/72598111
67. Add Binary   Easy   使用进位进行模拟   ddhttps://blog.youkuaiyun.com/fuxuemingzhu/article/details/77341154v
434. Number of Segments in a String   Easy   string.split()默认就是按照多个空格分割   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71194298
112. Path Sum   Easy   递归和迭代都能满足   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/71715810
205. Isomorphic Strings   Easy   分别看s到t的映射和t到s的映射是不是一一映射的   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/72127108
443. String Compression   Easy   使用Pos变量维护应该放到哪个位置，然后一次遍历统计次数就好了   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79183289
303. Range Sum Query - Immutable   Easy   保存每个位置的累积和   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79253036
438. Find All Anagrams in a String   Easy   滑动窗口，保存等长的子字符串中包含的字符数是否和另外一个相等   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79184109
20. Valid Parentheses   Easy   使用栈判断括号是否合法   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/72366868
840. Magic Squares In Grid   Easy   暴力判断每个9*9的格子是不是满足题意的河图   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80473253
141. Linked List Cycle   Easy   走两步走一步，看是否重合   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51297249
203. Remove Linked List Elements   Easy   递归解法不好想，但是代码很简单   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/77340945
234. Palindrome Linked List   Easy   利用一个数组保存所有的数字，然后判断数组是不是回文的。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/72597942
111. Minimum Depth of Binary Tree   Easy   DFS/BFS，其实DFS更难   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/48519035
290. Word Pattern   Easy   一一映射   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/72528424
155. Min Stack   Easy   使用辅助栈保存最小值   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79253237
219. Contains Duplicate II   Easy   使用字典保存出现的位置，当新的元素到来的时候，更新字典   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/77387169
941. Valid Mountain Array   Easy   两个while就可以了   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/84206380
88. Merge Sorted Array   Easy   从后向前进行遍历，每次找到大的往后移动   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/77444695
914. X of a Kind in a Deck of Cards   Easy   需要进行一个遍历，找到是否存在这个分组大小   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82914279
680. Valid Palindrome II   Easy   需要用到双指针，先找到第一个不相等的位置，然后去除左边或者右边，判断是否是回文   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79252779
687. Longest Univalue Path   Easy   定义的DFS是对过root的单臂进行循环，但是更新的结果是双臂，有点意思   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79248926
14. Longest Common Prefix   Easy   遍历最短的子串的每一位，看所有字符串在这一位上是不是相等的   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/77561186
686. Repeated String Match   Easy   重复NB/NA + 3次，看b是不是在a里   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79574835
122.Best Time to Buy and Sell Stock II   Easy   只要每天的比前面一天高，那么就买上并且卖掉即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70258549
28. Implement strStr()   Easy   循环加切片   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79254558
475. Heaters   Easy   找出最临近的距离   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79254295
754. Reach a Number   Easy   数学题，非常不喜欢   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/84556932
400. Nth Digit   Easy   数学计算第多少位   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/84559975
69. Sqrt(x)   Easy   二分查找或者牛顿法   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79254648
581. Shortest Unsorted Continuous Subarray   Easy   先排序，然后比较不等的位置   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79254454
190. Reverse Bits   Easy   翻转二进制再转成整数   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79254344
125. Valid Palindrome   Easy   过滤掉不是字母的字符，然后判断是不是回文即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79252936
874. Walking Robot Simulation   Easy   模拟整个过程即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82356556
532. K-diff Pairs in an Array   Easy   找绝对值出现等于k的次数，需要对k进行判断   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79255633
168. Excel Sheet Column Title   Easy   需要对26取余，并且做个判断，因为0\26对26取余的结果是一样的   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/51286857
189. Rotate Array   Easy   可以使用额外数组，也可使用递归原地翻转   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79258753
665. Non-decreasing Array   Easy   找到变小的位置，然后和再前面的数字进行判断，看是应该修改当前的还是前面的   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79264475
707. Design Linked List   Easy   自己实现链表，挺复杂的。可以使用list进行模拟，方便很多。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81026066
938. Range Sum of BST   Medium   需要根据根节点的值进行判断，邮编和左边需不需要继续寻找   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83961263
807. Max Increase to Keep City Skyline   Medium   分别找出行和咧的最大值，把每个位置增长到行列最大值的最小值   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79820383
535. Encode and Decode TinyURL   Medium   使用字典完成映射   https://blog.youkuaiyun.com/fuxuemingzhu
654. Maximum Binary Tree   Medium   找到最大值，然后数组切片   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79265180
701. Insert into a Binary Search Tree   Medium   递归解法，直接对当前节点进行操作！   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82385503
890. Find and Replace Pattern   Medium   判断是不是一一映射   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82014687
921. Minimum Add to Make Parentheses Valid   Medium   使用一个栈   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/83045871
797. All Paths From Source to Target   Medium   回溯法找路径   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79624149
861. Score After Flipping Matrix   Medium   把行进行翻转，按列统计1的个数即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/81118328
894. All Possible Full Binary Trees   Medium   使用两种循环遍历可能构成的左子树和右子树，每次构建新的root   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82084204
763. Partition Labels   Medium   使用字典保存每个字符最后出现的位置，如果一个区间内字符的最后位置的都在一起，那么就添加到结果里   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79265829
419. Battleships in a Board   Medium   直接数有多少小岛就行，判断小岛可以使用它的最左上角元素即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79403172
537. Complex Number Multiplication   Medium   复数运算，重点是分割字符串   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79266080
338. Counting Bits   Medium   i的二进制1个数等于i/2的二进制个数+i%2   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70806676
885. Spiral Matrix III   Medium   保留循环更新步数，很恶心   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82389223
791. Custom Sort String   Medium   统计次数，拼接成字符串   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79378688
442. Find All Duplicates in an Array   Medium   原地变成负数，如果已经是负数，那么说明出现了两次。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79275549
355. Design Twitter   Medium   使用优先级队列弹出最新的内容   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82155420
841. Keys and Rooms   Medium   可以使用DFS和BFS解决   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80476862
406. Queue Reconstruction by Height   Medium   先插入长得高的他们不会影响别人，然后在对应位置插入次高的   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/68486884
513. Find Bottom Left Tree Value   Medium   层次遍历，找出最后一层的第一个节点即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70161829
739. Daily Temperatures   Medium   使用一个栈，保存每个元素，如果后面的元素比较大，那么就已知出栈操作   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79285081
946. Validate Stack Sequences   Medium   使用栈进行模拟，无论如何都把当前的元素弹出，然后和弹出的元素进行比较，相等的话一直弹出   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/84495797
515. Find Largest Value in Each Tree Row   Medium   遍历每一层，找出最大值即可。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70183314
540. Single Element in a Sorted Array   Medium   可以使用很风骚的二分查找k,   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79275636
889. Construct Binary Tree from Preorder and Postorder Traversal   Medium   找到后序的倒数第二个元素就是右子树的根节点   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82391321
260. Single Number III   Medium   使用异或或者字典解决   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79434100
553. Optimal Division   Medium   这个题非常tricky，没意思   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79403723
647. Palindromic Substrings   Medium   判断回文，需要判断去掉两头字符之后是否仍然是回文，动态规划   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79433960
695. Max Area of Island   Medium   找到岛的数量，这个题可以使用BFS或者DFS的方法   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79182435
856. Score of Parentheses   Medium   可以使用栈和递归，这个题很巧妙，是个不错的题目   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/84956643
919. Complete Binary Tree Inserter   Medium   使用数组保存每个节点的指针，因为是完全二叉树，所以节点位置除以2就得到了它的父亲节点   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82958284
451. Sort Characters By Frequency   Medium   根据出现次数排序，然后构建新的字符串即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79437548
789. Escape The Ghosts   Medium   找出是否存在更小的曼哈顿距离   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80480462
94. Binary Tree Inorder Traversal   Medium   中序遍历本身很简单，但是这个递归的写法不好想   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79294461
865. Smallest Subtree with all the Deepest Nodes   Medium   定义递归函数：返回<最大深度,最大深度对应的节点>   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82432130
508. Most Frequent Subtree Sum   Medium   遍历求和，字典统计出现次数最多的所有元素   http://www.cnblogs.com/grandyang/p/6481682.html
526. Beautiful Arrangement   Medium   经典回溯法，要背会   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79431941
238. Product of Array Except Self   Medium   使用两次遍历，分别从左边和右边向中间靠拢   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79325534
712. Minimum ASCII Delete Sum for Two Strings   Medium   和LCS很接近的DP题目   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79822689
817. Linked List Components   Medium   判断当前节点在set中，但是下一个节点不在即可   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80479431
347. Top K Frequent Elements   Medium   使用字典统计次数，使用优先级队列实现排序   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79294073
462. Minimum Moves to Equal Array Elements II   Medium   找出中位数，然后求所有数字到中位数的距离和   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79437926
46. Permutations   Medium   经典回溯法   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79363903
495. Teemo Attacking   Medium   计算每次中毒的开始和结束时间   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79438658
22. Generate Parentheses   Medium   经典回溯法   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79362373
529. Minesweeper   Medium   扫雷游戏，使用DFS   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79462285
667. Beautiful Arrangement II   Medium   每次把后面最大数字放到前面来就能增加一种新的差值   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79437401
677. Map Sum Pairs   Medium   前缀树的题目，可以背一背   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79436619
547. Friend Circles   Medium   并查集的题目   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/70258103
565. Array Nesting   Medium   一直遍历就好了，使用一个visited数组，但不是回溯。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79460546
947. Most Stones Removed with Same Row or Column   Medium   需要使用并查集，非常考验抽象能力   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/84500642
858. Mirror Reflection   Medium   镜像反射，需要找规律，分偶数和奇数进行讨论   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/82432579
676. Implement Magic Dictionary   Medium   找到存不存在汉明间距是1   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79447934
781. Rabbits in Forest   Medium   对兔子出现次数进行统计，然后求一个公式。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79457764
769. Max Chunks To Make Sorted   Medium   从左到右遍历一次，时刻保持当前的最大值，如果当前最大值等于索引，那么chunck+1.   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/80482014
655. Print Binary Tree   Medium   先把二叉树构造出来，然后使用类似二分查找左右分治的方法。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79439026
208. Implement Trie (Prefix Tree)   Medium   构造字典树，是个好题，需要背会   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79388432
648. Replace Words   Medium   使用字典树或者拉链法求解   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79391682
421. Maximum XOR of Two Numbers in an Array   Medium   暴力求解会超时，需要使用异或的性质从最高位开始遍历。或者使用字典树。   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79473171
40. Combination Sum II   Medium   经典的回溯法，这个题需要背会   https://blog.youkuaiyun.com/fuxuemingzhu/article/details/79343638
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作者：负雪明烛
来源：优快云
原文：https://blog.youkuaiyun.com/fuxuemingzhu/article/details/85112591
版权声明：本文为博主原创文章，转载请附上博文链接！