Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).

Given the head of a singly linked list, return true if it is a palindrome.

Given an integer array nums, move all 0's to the end of it while maintaining the relative order of the non-zero elements. Note that you must do this in-place without making a copy of the array.

A message containing letters from A-Z can be encoded into numbers using the mapping. To decode an encoded message, all the digits must be grouped then mapped back into letters using the reverse of the mapping above (there may be multiple ways).

Given an m x n 2D binary grid, grid which represents a map of '1's (land) and '0's (water), return the number of islands.

A stack is an abstract data type that stores an ordered collection of items which follow first in last out (FILO) or last in first out (LIFO) principle; with two principal operations: push, which adds an item to the stack, and pop, which removes the most recently added item.

Dijkstra's algorithm is an algorithm for finding the shortest paths between nodes in a graph, which may represent, for example, road networks. It was conceived by computer scientist Edsger W. Dijkstra in 1956 and published three years later. The algorithm exists in many variants.

Autocomplete or suggestion or typeahead offers a number of possible values while typing. I am going to solve this problem using trie data structure and algorithm.

Web Worker API is a JavaScript web API for running multiple tasks simultaneously without affecting the performance of the apps.

The Beacon API is a JavaScript web API for sending data from the browser to the web server without expecting to get a response. It is used to send analytics, diagnostics, and logging data which doesn't need a response.

On a 2-dimensional grid, there are 4 types of squares. Return the number of 4-directional walks from the starting square to the ending square, that walk over every non-obstacle square exactly once.

Given n non-negative integers representing the histogram's bar height where the width of each bar is 1, find the area of largest rectangle in the histogram.

Calculate the Euclidean Distance for one dimensional, two dimensional, three dimensional in JavaScript. In mathematics, the Euclidean distance or Euclidean metric is the "ordinary" straight-line distance between two points in Euclidean space.

In an alien language, surprisingly they also use english lowercase letters, but possibly in a different order. The order of the alphabet is some permutation of lowercase letters.

Given a string, find the longest palindromic substring. We going to iterate each character in the string; and within that character, we expand and look for the longest palindrome. As we keep iterating, we only keep the longest palindrome.