A self-dividing number is a number that is divisible by every digit it contains. For example, 128 is a self-dividing number because 128 % 1 == 0, 128 ...

Let’s call an array A a mountain if the following properties hold: A.length >= 3There exists some 0 < i < A.length - 1 such that A[0] < A[ ...

Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are n ...

The Hamming distance between two integers is the number of positions at which the corresponding bits are different. Given two integers x and y, calcul ...

We are given an array A of N lowercase letter strings, all of the same length. Now, we may choose any set of deletion indices, and for each string, we ...

Given a string S that only contains “I” (increase) or “D” (decrease), let N = S.length. Return any permutation A of [0, 1, …, N] such that for all i = ...

There is a robot starting at position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0, 0) after it ...

Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image. To flip an image horizontally means t ...

Given an array A of non-negative integers, return an array consisting of all the even elements of A, followed by all the odd elements of A. You may re ...

Given an array of integers A sorted in non-decreasing order, return an array of the squares of each number, also in sorted non-decreasing order. Examp ...