# GeetCode Hub

### Easy

#### 1. Two Sum

Given an array of integers nums&nbsp;and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the <

### Medium

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum&nbsp;as a linked list. You may assume the two n

### Medium

#### 3. Longest Substring Without Repeating Characters

Given a string s, find the length of the longest substring without repeating characters. &nbsp; Example 1: Input: s = "abcabcbb" Output: 3 Explanation: The answer is "abc", wit

### Hard

#### 4. Median of Two Sorted Arrays

Given two sorted arrays nums1 and nums2 of size m and n respectively, return the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)). &nbsp; Example 1

### Medium

#### 5. Longest Palindromic Substring

Given a string s, return&nbsp;the longest palindromic substring in s. &nbsp; Example 1: Input: s = "babad" Output: "bab" Note: "aba" is also a valid answer. <str

### Medium

#### 6. ZigZag Conversion

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 I G Y I R And then read line by line: "PAHNAPLSIIGYIR"</co

### Easy

#### 7. Reverse Integer

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0. Assume t

### Medium

#### 8. String to Integer (atoi)

Implement the myAtoi(string s) function, which converts a string to a 32-bit signed integer (similar to C/C++'s atoi function). The algorithm for myAtoi(string s) is as follows: Read in and ignore any leading whitespace. Check if

### Easy

#### 9. Palindrome Number

Given an integer x, return true if x is palindrome integer. An integer is a palindrome when it reads the same backward as forward. For example, 121 is palindrome while 123 is not. &nbsp; <strong

### Hard

#### 10. Regular Expression Matching

Given an input string (s) and a pattern (p), implement regular expression matching with support for '.' and '*' where:&nbsp; '.' Matches any single character.​​​​ '*' Matches zero or m

### Medium

#### 11. Container With Most Water

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 the line i is at <