题目描述：Given two strings s and t, determine if they are isomorphic.Two strings are isomorphic if the characters in s can be replaced to get t.All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.For example,Given "egg", "add", return true.Given "foo", "ba...
Combination Sum IIGiven a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.Each number in C may only be used once in the combination.Note:All numbers (including target) will be positive integers.Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).The solution set ...
Given a binary tree and a sum, find all root-to-leaf paths where each path‘s sum equals the given sum.For example: Given the below binary tree and sum = 22, 5/ 4 8/ / 11 13 4/ \ / 7 2 5 1return[[5,4,11,2],[5,8,4,5] ] 解题思路：DFS，JAVA实现如下： static public List<List<Integer>> pathSum(TreeNode root, int sum) {List<List<Integer>> list ...
描述：给定一个字符串，请你找出其中不含有重复字符的 最长子串 的长度。输入: s = "abcabcbb" 输出: 3 解释: 因为无重复字符的最长子串是 "abc"，所以其长度为 3。输入: s = "bbbbb" 输出: 1 解释: 因为无重复字符的最长子串是 "b"，所以其长度为 1。思路一:利用滑动窗口：类似于一个队列,比如例题中的 abcav，进入这个窗口为 abc 满足题目要求，当再进入 a，队列变成了 abca，这时候不满足要求。所以，我们要移动这个队列,此时的...
题目描述：Given a sorted linked list, delete all duplicates such that each element appear only once.For example,Given 1->1->2, return 1->2.Given 1->1->2->3->3, return 1->2->3.代码如下：代码一，正常解法：/*** Definition for singly-linked list.* public class ListNode {* int val;* ListNode next;* ListNode(int x) { val = x; }* }*/ public class Solution {public ListNode deleteDuplicates(Lis...
题目：Given two words (start and end), and a dictionary, find all shortest transformation sequence(s) from start to end, such that:Only one letter can be changed at a timeEach intermediate word must exist in the dictionaryFor example,Given:start = "hit"end = "cog"dict = ["hot","dot","dog","lot","log"]Return [["hit","hot","dot","dog","cog"],["hit","hot","lot","log","cog"]]思路：先建立dict的邻接链表...
题目：Given a binary tree, return the postorder traversal of its nodes‘ values. For example: Given binary tree {1,#,2,3}, 12/3return [3,2,1]. Note: Recursive solution is trivial, could you do it iteratively? 题解：递归方法代码： 1 public void helper(TreeNode root, ArrayList<Integer> re){ 2 if(root==null) 3 return; 4 5 helper(root.left,re); 6 help...
【057-Insert Interval（插入区间）】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】原题 Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initially sorted according to their start times. Example 1: Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9]. Example 2: Given [1,2],[3,5]...
Copy List with Random PointerA linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.Return a deep copy of the list.https://leetcode.com/problems/copy-list-with-random-pointer/ 第一把直接暴力两轮遍历。第一轮遍历copy链表，用hash表记录下各个节点，第二乱遍历去赋值链表里的random对象。然后稍稍改进了一下，一次遍历里把能的找到...
题目：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 nodes in each of the two partitions.For example, Given 1->4->3->2->5->2 and x = 3, return 1->2->2->4->3->5. 题解： 这道题就是说给定一个x的值，小于x都放在大于等于x的前面，并且不改变链表之间node原始的相对位置。每次看...
Given n,how many structurally unique BST‘s (binarysearch trees) that store values 1...n? For example, Given n = 3, there are a total of 5 unique BST‘s. 1 3 3 2 1\ / / / \ 3 2 1 1 3 2/ / \ 2 1 2 3 给定一个n值，那么从1.2.3....N共N个数，能构建几棵二叉排序树。 解题思路就是：遍...
【024-Swap Nodes in Pairs（成对交换单链表的结点）】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】原题 Given a linked list, swap every two adjacent nodes and return its head. For example, Given 1->2->3->4, you should return the list as 2->1->4->3. Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed. 题目大意 给定一...
Given an array of integers, find two numbers such that they add up to a specific target number.The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.You may assume that each input would have exactly one solution.Input: numbers={2, 7, ...
Problem: Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would haveexactly one solution. For example, given array S = {-1 2 1 -4}, and target = 1.The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).Solution:此题与15题基本类似，甚至更简单一些，只需要比较和...
【114-Flatten Binary Tree to Linked List（二叉树转单链表）】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】原题 Given a binary tree, flatten it to a linked list in-place. For example, Given 1/ 2 5/ \ 3 4 6 The flattened tree should look like: 1 2 3 4 5 6题目大意 给定一棵二叉树，将它转成单链表，使用原地算法。 解题思...