Given the root of a binary tree, return the most frequent subtree sum. A subtree sum is the sum of all the node values in the subtree rooted at any node, including the node itself. If there is a tie, return all the subtree sums with the highest frequency.
You are given a binary grid of size m x n, where each cell is initially set to 0. The task is to design an algorithm that can randomly pick a cell that is still 0, flip it to 1, and ensure that all available cells are equally likely to be selected.
Given an array of strings strs, determine the length of the longest uncommon subsequence between them. An uncommon subsequence is a string that is a subsequence of one string but not the others. If no such subsequence exists, return -1.
Given an integer array nums and an integer k, return true if there exists a good subarray, otherwise return false. A good subarray is defined as a subarray whose length is at least 2 and the sum of its elements is a multiple of k.
Given an array of integers nums and an integer k, return the number of unique k-diff pairs in the array. A k-diff pair is a pair of integers (nums[i], nums[j]) where the absolute difference between the values of the pair is k, and i != j.
