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Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at that position.Your goal is to reac

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 move either down or right at any point in time. The robot is trying to reach the botto

Follow 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 respectively in the grid.For ex

Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.Note: You can only move either down or right at any

Given a positive integer num, write a function which returns True if num is a perfect square else False.Note: Do not use any built-in library function such as sqrt.Example 1:Input: 16 Returns: True E

You are climbing a stair case. It takes n steps to reach to the top.Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top? 思路：就是一个斐波那契数列，用动态规划解决class Solution

Implement pow(x, n). 思路：mark weiss allen的数据结构与算法分析第一章就有这个例子。思路就是递归。因为测试案例有n=-2147483648. 转成正的会超过int，所以用longlong保存正值。class Solution {public: double myPow(double x, int n) { if(n < 0)

Follow up for “Remove Duplicates”: What if duplicates are allowed at most twice?For example, Given sorted array nums = [1,1,1,2,2,3],Your function should return length = 5, with the first five elemen

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array [-2,1,-3,4,-1,2,1,-5,4], the contiguous subarray [4,-1,2,1] has the

Given a string s consists of upper/lower-case alphabets and empty space characters ’ ‘, return the length of last word in the string.If the last word does not exist, return 0.Note: A word is defined as

Given two sorted integer arrays nums1 and nums2, merge nums2 into nums1 as one sorted array.class Solution {public: void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) { int a

Given 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. 思路：动态规划。当n=7的时候，1为根结点，左边0个节点，右边6个节点和7为根结点对称，这种

Given an unsorted integer array, find the first missing positive integer.For example,Given [1,2,0] return 3,and [3,4,-1,1] return 2.Your algorithm should run in O(n) time and uses constant

Given two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have the same value.这个花了3ms/** * Defin

Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the absolute difference between i and j is at most k.cl

Given a singly linked list, determine if it is a palindrome.Follow up: Could you do it in O(n) time and O(1) space?/** * Definition for singly-linked list. * struct ListNode { * int val; *

Given a pattern and a string str, find if str follows the same pattern.Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str.Examples:

Write a function that takes a string as input and returns the string reversed.Example: Given s = “hello”, return “olleh”.class Solution {public: string reverseString(string s) { string t;

Write a function that takes a string as input and reverse only the vowels of a string.Example 1: Given s = “hello”, return “holle”.Example 2: Given s = “leetcode”, return “leotcede”.Note: The vowels

Given two arrays, write a function to compute their intersection.Example: Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].Note: Each element in the result must be unique. The result can be in

Given two arrays, write a function to compute their intersection.Example: Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2, 2].Note: Each element in the result should appear as many times as it

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.class Solution {public: int getSum(int a, int b) {

Given numRows, generate the first numRows of Pascal’s triangle.For example, given numRows = 5, Return [1], [1,1], [1,2,1], [1,3,3,1],[1,4,6,4,1]思路：动态规划，初始值：F[0,0]=1,F[1,0]=1,F[1,1]=1 F[i]

Given a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1.Examples:s = "leetcode"return 0.s = "loveleetcode",return 2.class Solution {public:

Given two strings s and t which consist of only lowercase letters.String t is generated by random shuffling string s and then add one more letter at a random position.Find the letter that was added in

Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.Note:The length of both num1 and num2 is < 5100.Both num1 and num2 contains only digits 0-9.Both

Given two non-negative integers num1 and num2 represented as strings, return the product of num1 and num2.Note:The length of both num1 and num2 is < 110. Both num1 and num2 contains only digits 0-9.

Given scores of N athletes, find their relative ranks and the people with the top three highest scores, who will be awarded medals: “Gold Medal”, “Silver Medal” and “Bronze Medal”.Example 1:Input: [5,

Given an integer, return its base 7 string representation.Example 1:Input: 100Output: "202"Example 2:Input: -7Output: "-10"Note: The input will be in range of [-1e7, 1e7].class Solution {public:

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 onl

Given an index k, return the kth row of the Pascal’s triangle.For example, given k = 3, Return [1,3,3,1].class Solution {public: vector<int> getRow(int rowIndex) { vector<int> ans;

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-b

Given a binary array, find the maximum number of consecutive 1s in this array.Example 1:Input: [1,1,0,1,1,1]Output: 3Explanation: The first two digits or the last three digits are consecutive 1s.

For a web developer, it is very important to know how to design a web page’s size. So, given a specific rectangular web page’s area, your job by now is to design a rectangular web page, whose length L

You are given two arrays (without duplicates) nums1 and nums2 where nums1’s elements are subset of nums2. Find all the next greater numbers for nums1’s elements in the corresponding places of nums2.The

Given a List of words, return the words that can be typed using letters of alphabet on only one row’s of American keyboard like the image below. Example 1:Input: ["Hello", "Alaska", "Dad", "Peace"]Ou

Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; oth

A binary watch has 4 LEDs on the top which represent the hours (0-11), and the 6 LEDs on the bottom represent the minutes (0-59).Each LED represents a zero or one, with the least significant bit on the

Find the sum of all left leaves in a given binary tree.Example: 3 / \ 9 20 / \ 15 7There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24./** * D

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 str