1277. Count Square Submatrices with All Ones

1277. Count Square Submatrices with All Ones Difficulty: Medium Related Topics: Array, Dynamic Programming Given a m * n matrix of ones and zeros, return how many square submatrices have all ones. Example 1: Input: matrix = [   [0,1,1,1],   [1,1,1,1],   [0,1,1,1] ] Output: 15 Explanation: There are 10 squares of side 1.Continue

368. Largest Divisible Subset

368. Largest Divisible Subset Difficulty: Medium Related Topics: Math, Dynamic Programming Given a set of distinct positive integers, find the largest subset such that every pair (Si, Sj) of elements in this subset satisfies: Si % Sj = 0 or Sj % Si = 0. If there are multiple solutions, return any subset is fine.Continue

1442. Count Triplets That Can Form Two Arrays of Equal XOR

1442. Count Triplets That Can Form Two Arrays of Equal XOR Difficulty: Medium Related Topics: Array, Math, Bit Manipulation Given an array of integers arr. We want to select three indices i, j and k where (0 <= i < j <= k < arr.length). Let’s define a and b as follows: a = arr[i] ^Continue

1222. Queens That Can Attack the King

1222. Queens That Can Attack the King Difficulty: Medium Related Topics: Array On an 8×8 chessboard, there can be multiple Black Queens and one White King. Given an array of integer coordinates queens that represents the positions of the Black Queens, and a pair of coordinates king that represent the position of the White King,Continue

969. Pancake Sorting

969. Pancake Sorting Difficulty: Medium Related Topics: Array, Sort Given an array of integers arr, sort the array by performing a series of pancake flips. In one pancake flip we do the following steps: Choose an integer k where 1 <= k <= arr.length.Reverse the sub-array arr[1…k]. For example, if arr = [3,2,1,4] and we performedContinue

1338. Reduce Array Size to The Half

1338. Reduce Array Size to The Half Difficulty: Medium Related Topics: Array, Greedy Given an array arr.  You can choose a set of integers and remove all the occurrences of these integers in the array. Return the minimum size of the set so that at least half of the integers of the array are removed.Continue

372. Super Pow

372. Super Pow Difficulty: Medium Related Topics: Math Your task is to calculate ab mod 1337 where a is a positive integer and b is an extremely large positive integer given in the form of an array. Example 1: Input: a = 2, b = [3] Output: 8 Example 2: Input: a = 2, bContinue

357. Count Numbers with Unique Digits

357. Count Numbers with Unique Digits Difficulty: Medium Related Topics: Math, Dynamic Programming, Backtracking Given a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x < 10n. Example: Input: 2 Output: 91 Explanation: The answer should be the total numbers in the range of 0 ≤ x < 100,  Continue

145. Binary Tree Postorder Traversal

145. Binary Tree Postorder Traversal Difficulty: Medium Related Topics: Stack, Tree Given the root of a binary tree, return the postorder traversal of its nodes’ values. Follow up: Recursive solution is trivial, could you do it iteratively? Example 1: Input: root = [1,null,2,3] Output: [3,2,1] Example 2: Input: root = [] Output: [] Example 3: Input:Continue

986. Interval List Intersections

986. Interval List Intersections Difficulty: Medium Related Topics: Two Pointers Given two lists of closed intervals, each list of intervals is pairwise disjoint and in sorted order. Return the intersection of these two interval lists. (Formally, a closed interval [a, b] (with a <= b) denotes the set of real numbers x with a <= x <=Continue