大力拜

Implement atoi to convert a string to an integer. Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input ca

Reverse digits of an integer. Example1: x = 123, return 321 Example2: x = -123, return -321 click to show spoilers. Have you thought about this? Here are some good questions to ask before c

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility) P A H N A P L S I

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: Elements in a triplet (a,b,c

There are two sorted arrays nums1 and nums2 of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)). 这是一道非常经典的题。这题更通用的形式是，给定

Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. class Solution { public: string intToRoman(int num) { map mp = {{1000,"M"},{9

Write a function to find the longest common prefix string amongst an array of strings. class Solution { public: string longestCommonPrefix(vector& strs) { if(strs.size()==0) return "";

Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. class Solution { public: int romanToInt(string s) { unordered_map mp = {{"M",

Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Fin

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. Fo

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 have exact