You are given two integer arrays, pushed and popped, each containing distinct values. The arrays represent the order of elements being pushed onto and popped from an initially empty stack. Your task is to determine if it is possible to obtain the popped sequence from the pushed sequence through a series of valid stack push and pop operations.
You are given a set of stones placed on a 2D plane at various integer coordinate points. A stone can be removed if it shares the same row or column as another stone that has not been removed yet. Your task is to determine the maximum number of stones that can be removed from the plane by performing valid operations.
You are given an array of tokens and an initial amount of power. The goal is to maximize the score by playing the tokens strategically. In each turn, you can either play a token face-up or face-down. Playing a token face-up costs you power but increases your score, while playing a token face-down gains you power but decreases your score. Your task is to determine the maximum score you can achieve after playing the tokens.
Given an array of 4 digits, your task is to form the latest possible 24-hour time using each digit exactly once. The time is represented in the format ‘HH:MM’ where ‘HH’ is between 00 and 23, and ‘MM’ is between 00 and 59. If no valid time can be formed, return an empty string.
You are given an array of integers, where each integer represents a unique card in a deck. The deck can be shuffled into any order, and the goal is to reorder it such that the cards are revealed in increasing order. To do this, you repeatedly reveal the top card and move the next card to the bottom of the deck until all cards are revealed. The problem is to return the order of cards that would reveal them in increasing order.
You are given the roots of two binary trees. A flip operation consists of choosing any node and swapping its left and right child subtrees. A tree X is flip equivalent to tree Y if and only if we can make tree X equal to tree Y by performing some flip operations on X. Your task is to determine if the two trees are flip equivalent.