You are given an m x n grid where each cell represents a street. The streets have different connections between neighboring cells. Starting from the top-left corner of the grid, you need to find if there exists a valid path to the bottom-right corner, following the direction of the streets.
You are given an undirected tree with n vertices numbered from 0 to n-1. Some vertices in this tree contain apples. Each edge in the tree requires 1 second to traverse. Starting at vertex 0, determine the minimum time required to collect all apples and return to vertex 0. The tree structure is described by the array edges, where edges[i] = [ai, bi] indicates an edge between vertices ai and bi. Additionally, the array hasApple specifies whether a vertex contains an apple (true) or not (false).
Given the root of a binary tree, a node is considered ‘good’ if in the path from the root to that node, there are no nodes with a value greater than the node itself. Return the total number of good nodes in the tree.
You are given a binary tree where each node contains a digit from 1 to 9. A path from the root to a leaf node is considered pseudo-palindromic if at least one permutation of the node values in the path can form a palindrome. Your task is to return the number of pseudo-palindromic paths in the tree.
You are given a set of courses numbered from 0 to numCourses - 1 and a list of prerequisites. Each prerequisite is a pair [ai, bi], indicating that you must complete course ai before course bi. For a series of queries, where each query asks whether a specific course is a prerequisite for another, you are tasked with determining whether each query is true or false.
You are given n cities and n - 1 roads, forming a tree structure. The roads have been directed, and some roads may need to be reoriented to ensure all cities can reach the capital city (city 0). Your task is to determine the minimum number of road reorientations required to make it possible for each city to reach city 0.