Renoler的博客

Link: https://leetcode.com/problems/diagonal-traverse/Solution 1:矩阵最外围的数字是每一次traverse slices的head偶数位的traverse方向是up right奇数位的方向是down left重点是要找到最外围数字的遍历方法class Solution { public int[] findDiag...

Problem:https://leetcode.com/problems/plus-one/Solution: Copy arrayclass Solution { public int[] plusOne(int[] digits) { int l = digits.length; for(int i = l-1; i >= 0; i--) {...

Problem: https://leetcode.com/problems/largest-number-at-least-twice-of-others/class Solution { public int dominantIndex(int[] nums) { int max = 0; int max_idx = 0; for(in...

Problems: https://leetcode.com/problems/find-pivot-index/class Solution { public int pivotIndex(int[] nums) { if(nums.length == 0) { return -1; } else { in...

Problems: https://leetcode.com/problems/reorder-data-in-log-files/思路：把log分开考虑，从第二个string开始看是否是digit，分为digit和letter两个listletterList重写sort方法，从第二个string开始按照字母顺序进行排序，需要注意的是如果字母顺序完全相同，则考虑index的字母排序Solu...

Problems: https://leetcode.com/problems/add-strings/Solution:十进制进位计算class Solution { public String addStrings(String num1, String num2) { StringBuilder sb = new StringBuilder(); ...

Problem: https://leetcode.com/problems/convert-binary-search-tree-to-sorted-doubly-linked-list/Soluiton:使用inorder traversal读取值，读出来的node和cur double linked最后再把dummy node删除class Solution { public...

Problem: https://leetcode.com/problems/copy-list-with-random-pointer/Solution1:Use HashMap to store the copy of original nodeCreate a new list to store the copyRandom pointer points to copyclass ...

Problem: https://leetcode.com/problems/read-n-characters-given-read4/Solution for call one time:read4读4个 -> 4个一组放入buf中 -> read4继续读 -> 直到读满n个或者字符串已经读完（不满n个）public class Solution extends Rea...

Problems: https://leetcode.com/problems/add-and-search-word-data-structure-design/Solution:本题如果使用hashmap的话，在search时将会很难应付“…ab”的情况class WordDictionary { class TrieNode { boolean isTrie;...

Problems: https://leetcode.com/problems/implement-trie-prefix-tree/Solution:class Trie { // TrieNode是Trie的基本元素 // isTrie判断该字符是否是prefix结束 // children记录字符的child class TrieNode { boolean...

Problems: https://leetcode.com/problems/merge-k-sorted-lists/Solution1:使用priorityQueue，将每个list的第一个值放入queue中，小的作为head，在取出的同时把node的下一个放入queue中需要注意的是，要不断check node.next是否为空class Solution { public...

Problems: https://leetcode.com/problems/sliding-window-maximum/Solution:利用deque，deque peek存储当前window内最大的值，实现的方法为：当添加新unit时检查val，如果大于当前queue内的val，则将原unit pop出来，然后再加入新的unit当添加的unit小于原来的val，则直接加入deq...

Problems:https://leetcode.com/problems/search-a-2d-matrix-ii/Solution:鉴于matrix的特性，binary search已经不适用，为了迭代方便，从逆对角线的两端下手（任意选一端即可）class Solution { public boolean searchMatrix(int[][] matrix, int ...

Problems:https://leetcode.com/problems/search-a-2d-matrix/Solution1:class Solution { public boolean searchMatrix(int[][] matrix, int target) { // 矩阵为空，需要注意的是depth和width都需要判断 if(mat...

Problems: https://leetcode.com/problems/lru-cache/Solution:结合double linkedlist和hashmaphashmap用于存储并且快速查找double linkedlist用于快速删除/增加class LRUCache { // linkedlist中node的设定 class Node { ...

Problems: https://leetcode.com/problems/valid-palindrome-ii/Solution:若不回文s [ i : j ]，比较s [ i+1 : j ]和s [ i : j+1 ]class Solution { public boolean isPalindrome(String s) { for (int i = 0...

Problems: https://leetcode.com/problems/first-bad-version/Solution:Binary Searchpublic class Solution extends VersionControl { public int firstBadVersion(int n) { int l = 1; int...

Problems: https://leetcode.com/problems/binary-tree-right-side-view/Solution1:level order，将每层分好后取出最右的值class Solution { List<ArrayList<Integer>> levels = new ArrayList<>(); ...

Preorder: https://leetcode.com/problems/binary-tree-preorder-traversal/Inorder: https://leetcode.com/problems/binary-tree-inorder-traversal/Postorder: https://leetcode.com/problems/binary-tree-posto...

还需要进一步理解Solution1:class Solution { Random rand; int[] a; public Solution(int[] w) { this.rand = new Random(); this.a = new int[w.length]; a[0] = w[0]; for...

Problem: https://leetcode.com/problems/two-sum/solution/Solution1:Brute Forceclass Solution { public int[] twoSum(int[] nums, int target) { int[] result = new int[2]; for (int i...

Problem: https://leetcode.com/problems/integer-to-english-words/Solution:重点在于如何把长数分割成小的部分考虑（分别为billion，million，thousand，各部分均有三位数字）class Solution { public String single(int num) { switch...

Problems: https://leetcode.com/problems/continuous-subarray-sum/Solution1:利用sum存储到第 i 位的sum注意计算diff时subarray长度至少为2class Solution { public boolean checkSubarraySum(int[] nums, int k) { ...

Problems: https://leetcode.com/problems/monotonic-array/Solution1:添加新方法判断class Solution { public boolean isMonotonic(int[] A) { return isIncreasing(A) || isDecreasing(A); } ...

Problems: https://leetcode.com/problems/merge-sorted-array/Solution1:Merge from startclass Solution { public void merge(int[] nums1, int m, int[] nums2, int n) { //因为要对nums1进行改变，所以先将num...

ProblemL: https://leetcode.com/problems/contains-duplicate/Solution1:class Solution { public boolean containsDuplicate(int[] nums) { // 暴力枚举 for(int i = 0; i < nums.length; i++...

Problems: https://leetcode.com/problems/alien-dictionary/Solution:Topological Sort建立拓扑图并寻找所有字符的入度(buildGraph)，再寻找入度为0的字符取出，邻接字符入度减一(bfs)class Solution { public String alienOrder(String[] words...

Problems: https://leetcode.com/problems/word-search/Solution:DFSclass Solution { public boolean exist(char[][] board, String word) { if(board == null) { return false; ...

Problems: https://leetcode.com/problems/word-break/Solution1Brute force: check all possible substringsclass Solution { public boolean wordBreak(String s, List<String> wordDict) { ...

Problems: https://leetcode.com/problems/intersection-of-two-arrays-ii/Solution1:Using map只需要存储nums1的map对于输出，不需要另外创建数组，而是直接重写nums1class Solution { public int[] intersect(int[] nums1, int[] n...

Problems: https://leetcode.com/problems/remove-invalid-parentheses/Solution:class Solution { public List<String> removeInvalidParentheses(String s) { char[] arr = s.toCharArray();...

Problems: https://leetcode.com/problems/intersection-of-two-arrays/Solution1:Using two setsclass Solution { public int[] set_intersection(HashSet<Integer> s1, HashSet<Integer> s2) {...

Problems: https://leetcode.com/problems/merge-intervals/Solution:class Solution { public int[][] merge(int[][] intervals) { List<int[]> res = new ArrayList<>(); if(in...

Problems: https://leetcode.com/problems/task-scheduler/Solution1:k为最高频字母出现的次数，n为interval数，p为最高频率相同的字母个数理想状态下的结果ans = (k-1) * (n+1) + p;class Solution { public int leastInterval(char[] tasks, i...

Problem: https://leetcode.com/problems/subarray-sum-equals-k/Solution1:利用累计和class Solution { public int subarraySum(int[] nums, int k) { // 计算累计和 int[] sum = new int[nums.length...

Problems:https://leetcode.com/problems/valid-palindrome/Solution:class Solution { public boolean isPalindrome(String s) { // 将字符小写化 String ls = s.toLowerCase(); // 删除不是数字/字...

Problem: https://leetcode.com/problems/maximum-gap/Solution: still has run time error.利用桶排序定义好bucket的大小和个数存数找到bucket中的max和min比较bucket[i].min 和 bucket[i-1].max 的差，即相邻两数的最大差class Bucket { i...

Problems:https://leetcode.com/problems/longest-consecutive-sequence/Solution1:动态规划算法首先对数组进行排序，数组dp[]存储到到当前位置的最大连续次数，设定dp的初始值为1若前后差值为1，则dp加一，若前后差值为0，则dp不变最终输出dp的最大值class Solution { public in...

Problem:https://leetcode.com/problems/increasing-triplet-subsequence/submissions/Solution:class Solution { public boolean increasingTriplet(int[] nums) { int small = Integer.MAX_VALUE;...