编程小白的进阶之路

LeetCode 63.Unique Paths IIFollow up for “Unique Paths”:Now consider if some obstacles are added to the grids. How many unique paths would there be?An obstacle and empty space is marked as 1 and 0 res

LeetCode 108.Convert Sorted Array to Binary Search Tree题目来源：https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/description/Given an array where elements are sorted in ascending or

LeetCode 110.Balanced Binary TreeGiven a binary tree, determine if it is height-balanced.For this problem, a height-balanced binary tree is defined as: a binary tree in which the depth of the two sub

LeetCode Symmetric Tree题目来源 https://leetcode.com/problems/symmetric-tree/description/Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this bi

LeetCode 100 Same Tree题目来源：https://leetcode.com/problems/same-tree/description/Given two binary trees, write a function to check if they are the same or not.Two binary trees are considered the same if

LeetCode 53. Maximum Subarray题目来源：https://leetcode.com/problems/maximum-subarray/description/Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For

Leetcode 81 Search in Rotated Sorted Array II题目来源：https://leetcode.com/problems/search-in-rotated-sorted-array-ii/description/ Follow up for “Search in Rotated Sorted Array”: What if duplicates a

LeetCode 34. Search for a Range题目来源：https://leetcode.com/problems/search-for-a-range/description/Given an array of integers sorted in ascending order, find the starting and ending position of a given t

LeetCode 35 Search Insert Position题目来源：https://leetcode.com/problems/search-insert-position/description/Given a sorted array and a target value, return the index if the target is found. If not, return

LeetCode 109. Convert Sorted List to Binary Search Tree题目来源：https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/description/Given a singly linked list where elements are sorte

LeetCode 112 Path Sum题目来源：https://leetcode.com/problems/path-sum/description/Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the pa

LeetCode 144.Binary Tree Preorder TraversalGiven a binary tree, return the preorder traversal of its nodes’ values.For example: Given binary tree [1,null,2,3], 1 \ 2 / 3return [1,2,

LeetCode 62 Unique Paths题目链接：https://leetcode.com/problems/unique-paths/description/A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below).The robot can only m

LeetCode 64 .Minimum Path Sum题目链接：https://leetcode.com/problems/minimum-path-sum/description/Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimiz

LeetCode 98.Validate Binary Search TreeGiven a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:The left subtree of a node contains only nodes with k

LeetCode 95.Unique Binary Search Trees II题目链接：https://leetcode.com/problems/unique-binary-search-trees-ii/description/Given an integer n, generate all structurally unique BST’s (binary search trees) th

LeetCode 96.Unique Binary Search TreesGiven n, how many structurally unique BST’s (binary search trees) that store values 1…n?For example, Given n = 3, there are a total of 5 unique BST’s. 1

LeetCode 69. Sqrt(x)Implement int sqrt(int x).Compute and return the square root of x.x is guaranteed to be a non-negative integer.Example 1:Input: 4Output: 2Example 2:Input: 8Output: 2Explanation:

LeetCode 145. Binary Tree Postorder TraversalGiven a binary tree, return the postorder traversal of its nodes’ values.For example: Given binary tree [1,null,2,3], 1 \ 2 / 3return [3

LeetCode 94. Binary Tree Inorder TraversalGiven a binary tree, return the inorder traversal of its nodes’ values.For example: Given binary tree [1,null,2,3], 1 \ 2 / 3return [1,3,2]

LeetCode 3. Longest Substring Without Repeating CharactersGiven a string, find the length of the longest substring without repeating characters.Examples:Given "abcabcbb", the answer is "abc", which the

1.Sort a linked list in O(n log n) time using constant space complexity.使用合并排序对单链表进行排序，时间复杂度为O(nlogn),使用插入排序对单链表进行排序，时间复杂度为O(n2);public class Sort_list { public ListNode findMiddle(ListNode head){

Given a linked list, remove the n th node from the end of list and return its head.For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linked

合并两个有序链表：package leetcode;import java.util.List;public class MergeTwoSortedList { public ListNode MergeTwoSortedList(ListNode l1,ListNode l2) { // TODO Auto-generated constructor stub

Reverse a linked list from position m to n. Do it in-place and in one-pass.For example: Given1->2->3->4->5->NULL, m = 2 and n = 4,return1->4->3->2->5->NULL.Note: Given m, n satisfy the following con

package leetcode;Given a sorted linked list, delete all duplicates such that each element appear only once. For example, Given1->1->2, return1->2. Given1->1->2->3->3, return1->2->3.题意：把重复的元素删除。

remove-duplicates-from-sorted-list:Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list. For example, Given1->2->3->3->4->4->

ParttiTion List 划分链表Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.You should preserve the original relative order of the n

合并两个有序链表：package leetcode;import java.util.List;public class MergeTwoSortedList { public ListNode MergeTwoSortedList(ListNode l1,ListNode l2) { // TODO Auto-generated constructor stub

Recorder_Listhttps://www.nowcoder.com/questionTerminal/3d281dc0b3704347846a110bf561ef6bGiven a singly linked list L: L 0→L 1→…→L ​ n-1→L n, reorder it to: L 0→L ​ n →L 1→L

Given a linked list, determine if it has a cycle in it.Follow up: Can you solve it without using extra space?判断一个单链表中是否存在环：采用快慢指针方法，若慢指针和快指针中间相遇，则一定存在环。public class Circle_List { public boolean ha

Given a linked list, return the node where the cycle begins. If there is no cycle, returnnull.Follow up: Can you solve it without using extra space?找出单链表中环开始的结点：（1）同Circle——List，使用快慢指针判断是否存在环，并找到两指针相遇

155. Min Stack题目链接：https://leetcode.com/problems/min-stack/description/Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.push(x) – Push element x onto st

LeetCode 2 Add Two Numbers题目链接：https://leetcode.com/problems/add-two-numbers/description/You are given two non-empty linked lists representing two non-negative integers. The digits are stored in revers

Count and SayThe count-and-say sequence is the sequence of integers with the first five terms as following:1. 12. 113. 214. 12115. 1112211 is read off as "one 1" or 11. 11 is r

20 Valid ParenthesesGiven a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.The brackets must close in the correct order, "()" and "()[]{}"

Two Sum和Three Sum1.Given an array of integers, return indices of the two numbers such that they add up to a specific target.You may assume that each input would have exactly one solution, and you may n

Longest Common PrefixWrite a function to find the longest common prefix string amongst an array of strings.方法一：public String longestCommonPrefix(String[] strs) { int n=strs.length,j;

卡特兰数的应用：（1）n对括号正确匹配数目：给定n对括号，求括号正确配对的字符串数，例如：0对括号：[空序列] 1种可能1对括号：() 1种可能2对括号：()() (()) 2种可能3对括号：((())) ()(()) ()()() (())() (()()) 5种可能那么问题来了，n对括号有多少种正确配对的可能呢？考虑n对括号时的任意一种配对方案，最后一个右括号有唯一的与之匹配的左括号，于是有唯一

1.Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.（mininum-depth-of-binary-tree）:二叉树class S