DescriptionGiven a binary search tree, write a function kthSmallest to find the kth smallest element in it. Note:You may assume k is always valid, 1 ≤ k ≤ BST’s total elements. The original problem is

DescriptionFollow 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 t

DescriptionThe original problem is here. The original code is here.

DescriptionGiven a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place. The original problem is here. The original code is here.

DescriptionYou are given an n x n 2D matrix representing an image. Rotate the image by 90 degrees (clockwise). Follow up:Could you do this in-place? The original problem is here. The original code is

DescriptionGiven an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the i

DescriptionSay you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the

DescriptionA 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 re

DescriptionGiven an array where elements are sorted in ascending order, convert it to a height balanced BST. The original problem is here. The original code is here.

DescriptionGiven 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. 1 3 3 2 1