## Valid Palindrome

QUESTION Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. This question is provided by Leetocode.

QUESTION Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. This question is provided by Leetocode.

QUESTION Follow 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 the grid. This question is provided by Leetocode.

QUESTION A 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 reach the bottom-right corner of the grid (marked ‘Finish’ in the diagram below). How many Read the full article…

QUESTION Given n, generate all structurally unique BST’s (binary search trees) that store values 1…n. This question is provided by Leetocode.

QUESTION Given an array of integers, find two numbers such that they add up to a specific target number. The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are Read the full article…

QUESTION Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). This question is provided by Leetocode.

QUESTION Given a 2D board containing ‘X’ and ‘O’, capture all regions surrounded by ‘X’. A region is captured by flipping all ‘O’s into ‘X’s in that surrounded region . This question is provided by Leetocode.

QUESTION Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number. An example is the root-to-leaf path 1->2->3 which represents the number 123. Find the total sum of all root-to-leaf numbers. This question is provided by Leetocode.

QUESTION Given a collection of integers that might contain duplicates, S, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. This question is provided by Leetocode.

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