本文从 Leetcode 中精选大概 200 左右的题目,去除了某些繁杂但是没有多少算法思想的题目,同时保留了面试中经常被问到的经典题目. 算法思想 双指针 排序 贪心思想 二分查找 分治 搜索 动态规划 数学 数据结构相关 链表 树 栈和队列 哈希表 字符串 数组与矩阵 图 位运算 参考资料 Leetcode Weiss M A, 冯舜玺. 数据结构与算法分析——C 语言描述[J]. 2004. Sedgewick R. Algorithms[M]. Pearson Education Ind…

前言 本目录将不断更新记录leetcode的刷题日记. 二叉树 序号 标题 难度 标签 1 108 将有序数组转换为二叉搜索树 简单 树.深度优先搜索 2 538 把二叉搜索树转换为累加树 简单 树 3 102 二叉树的层序遍历 中等 树.广度优先搜索.深度优先搜索 4 103 二叉树的锯齿形层次遍历 中等 栈.树.广度优先搜索 5 111 二叉树的最小深度 简单 树.深度优先搜索.广度优先搜索 6 543 二叉树的直径 简单 树 7 101 对称二叉树 简单 树.深度优先搜索.广度优先搜索 8…

数组 [1]999. 车的可用捕获量 [2]989. 数组形式的整数加法…

0001. 两数之和(Java) 0003. 无重复字符的最长子串(Java) 0172. 阶乘后的零 (Java) 0287. 寻找重复数(Java)…

1  leetcode-69. x 的平方根   https://www.cnblogs.com/shoshana-kong/p/9745424.html 2. 3. 4. 5. 6.…

Given a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST. Example: Input: The root of a Binary Search Tree like thi…

Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not. You need to merge them into a new binary tree. The merge rule is that if two nodes overlap, then…

You need to construct a string consists of parenthesis and integers from a binary tree with the preorder traversing way. The null node needs to be represented by empty parenthesis pair "()". And you need to omit all the empty parenthesis pairs t…

Design and implement a data structure for a compressed string iterator. It should support the following operations: next and hasNext. The given compressed string will be in the form of each letter followed by a positive integer representing the numbe…

Suppose Andy and Doris want to choose a restaurant for dinner, and they both have a list of favorite restaurants represented by strings. You need to help them find out their common interest with the least list index sum. If there is a choice tie betw…

We define a harmonious array is an array where the difference between its maximum value and its minimum value is exactly 1. Now, given an integer array, you need to find the length of its longest harmonious subsequence among all its possible subseque…

Given an integer array with even length, where different numbers in this array represent different kinds of candies. Each number means one candy of the corresponding kind. You need to distribute these candies equally in number to brother and sister.…

Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node's descendants. The tree s could also be considere…

In MATLAB, there is a very useful function called 'reshape', which can reshape a matrix into a new one with different size but keep its original data. You're given a matrix represented by a two-dimensional array, and two positive integers r and c rep…

Given a binary tree, return the tilt of the whole tree. The tilt of a tree node is defined as the absolute difference between the sum of all left subtree node values and the sum of all right subtree node values. Null node has tilt 0. The tilt of the …

Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longestpath between any two nodes in a tree. This path may or may not pass through the root. Example:Given a binary tr…

Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes. Example: Input: 1 \ 3 / 2 Output: 1 Explanation: The minimum absolute difference is 1, which is the difference between 2 and 1…

Given a binary search tree (BST) with duplicates, find all the mode(s) (the most frequently occurred element) in the given BST. Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than or equal to the nod…

Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation. Note: The given integer is guaranteed to fit within the range of a 32-bit signed integer. You could assume no leading ze…

The Hamming distance between two integers is the number of positions at which the corresponding bits are different. Given two integers x and y, calculate the Hamming distance. Note:0 ≤ x, y < 231. Example: Input: x = 1, y = 4 Output: 2 Explanation: 1…

Assume you are an awesome parent and want to give your children some cookies. But, you should give each child at most one cookie. Each child i has a greed factor gi, which is the minimum size of a cookie that the child will be content with; and each…

You are given a binary tree in which each node contains an integer value. Find the number of paths that sum to a given value. The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to…

Given an integer, write an algorithm to convert it to hexadecimal. For negative integer, two’s complement method is used. Note: All letters in hexadecimal (a-f) must be in lowercase. The hexadecimal string must not contain extra leading 0s. If the nu…

Find the sum of all left leaves in a given binary tree. Example: 3 / \ 9 20 / \ 15 7 There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24. 题目标签:Tree 这道题目给了我们一个二叉树,让我们找到所有左子叶之和.这里需要另外一个function - sumLeftLeaves 还要一…

Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -. Example:Given a = 1 and b = 2, return 3. 题目标签:Bit Manipulation 这道题目让我们做两数之和,当然包括负数,而且不能用+,-等符号.所以明显是让我们从计算机的原理出发,运用OR,AND,XOR等运算法则.一开始自己想的如果两个数都是正数,那么很简单,…

Given a stream of integers and a window size, calculate the moving average of all integers in the sliding window. For example, MovingAverage m = new MovingAverage(3); m.next(1) = 1 m.next(10) = (1 + 10) / 2 m.next(3) = (1 + 10 + 3) / 3 m.next(5) = (1…

Given an integer (signed 32 bits), write a function to check whether it is a power of 4. Example:Given num = 16, return true. Given num = 5, return false. Follow up: Could you solve it without loops/recursion? 题目标签:Bit Manipulation 这道题目让我们判断一个数字是不是4的…

Given a nested list of integers, return the sum of all integers in the list weighted by their depth. Each element is either an integer, or a list -- whose elements may also be integers or other lists. Example 1:Given the list [[1,1],2,[1,1]], return …

You are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 stones. The one who removes the last stone will be the winner. You will take the first turn to remove th…

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements. For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0]. Note: You…