Write a function that reverses a string. The input string is given as an array of characters <code>s</code>.

Write a function that reverses a string. The input string is given as an array of characters `s`.

You are given an <code>n x n</code> 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

You are given an `n x n` 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

Given an array of integers <code>nums</code> and an integer <code>target</code>, return indices of the two numbers such that they add up to target.

Given an array of integers `nums` and an integer `target`, return indices of the two numbers such that they add up to target.

Given an integer array <code>nums</code>, move all 0's to the end of it while maintaining the relative order of the non-zero elements.

Given an integer array `nums`, move all 0's to the end of it while maintaining the relative order of the non-zero elements.

Given two integer arrays <code>nums1</code> and <code>nums2</code>, return an array of their intersection. Each element in the result must appear as many times as it shows in both arrays and you may return the result in any order.

Given two integer arrays `nums1` and `nums2`, return an array of their intersection. Each element in the result must appear as many times as it shows in both arrays and you may return the result in any order.

Given a non-empty array of integers <code>nums</code>, every element appears twice except for one. Find that single one. 
You must implement a solution with a linear runtime complexity and use only constant extra space.

Given a non-empty array of integers `nums`, every element appears twice except for one. Find that single one.
You must implement a solution with a linear runtime complexity and use only constant extra space.

Given an integer array <code>nums</code>, return <code>true</code> if any value appears at least twice in the array, and return <code>false</code> if every element is distinct.

Given an integer array `nums`, return `true` if any value appears at least twice in the array, and return `false` if every element is distinct.

Coding Questions