Given a binary tree, find its minimum depth.
Given an array of strings strs, group the anagrams together. You can return the answer in any order.
You are given an m x n binary matrix grid. An island is a group of 1's connected 4-directionally. Return the maximum area of an island in grid.
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.
You are given two binary trees root1 and root2. Return the merged tree.
Problem: Given an integer array nums where the elements are sorted in ascending order, convert it to a height-balanced binary search tree.
Return true if the tree has a root-to-leaf path such that adding up all the values along the path equals targetSum.
Given the root of a binary tree, return the level order traversal of its nodes' values. (i.e., from left to right, level by level).
Given the root of a binary tree, return the zigzag level order traversal of its nodes' values.
Return the time it takes for all the n nodes to receive the signal. If it is impossible for all the n nodes to receive the signal, return -1.
Given the head of a linked list, return the node where the cycle begins. If there is no cycle, return null.