Write a function that takes an unsigned integer and returns the number of ‘1’ bits it has (also known as the Hamming weight).

Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.

Given a 2D board containing 'X' and 'O' (the letter O), capture all regions surrounded by 'X'.

Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.

Implement a basic calculator to evaluate a simple expression string.

You are playing the following Bulls and Cows game with your friend: You write down a number and ask your friend to guess what the number is. Each time your frie...

Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2).

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.

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.