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The problem You are given an n x n integer matrix grid where each value grid[i][j] represents the elevation at that point (i, j). It starts raining, and water gradually rises over time. At time t, the water level is t, meaning any cell with elevation less than or equal to t is submerged or reachable. You can swim from a square to another 4-directionally adjacent square if and only if the elevation of both squares individually is at most t. You can swim infinite distances in zero time. Of course, you must stay within the boundaries of the grid during your swim. ...

The problem You are given an array points representing integer coordinates of some points on a 2D plane, where points[i] = [xi, yi]. The cost of connecting two points [xi, yi] and [xj, yj] is the Manhattan distance between them: |xi - xj| + |yi - yj|, where |val| denotes the absolute value of val. Return the minimum cost to make all points connected. All points are connected if there is exactly one simple path between any two points. ...

The problem You are given a list of airline tickets where tickets[i] = [from_i, to_i] represent the departure and the arrival airports of one flight. Reconstruct the itinerary in order and return it. All of the tickets belong to a man who departs from "JFK", thus, the itinerary must begin with "JFK". If there are multiple valid itineraries, you should return the itinerary that has the smallest lexical order when read as a single string. ...

The problem You are given a network of n nodes, labeled from 1 to n. You are also given times, a list of travel times as directed edges times[i] = (ui, vi, wi), where ui is the source node, vi is the target node, and wi is the time it takes for a signal to travel from source to target. We will send a signal from a given node k. Return the minimum 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. ...

The problem A transformation sequence from word beginWord to word endWord using a dictionary wordList is a sequence of words beginWord -> s1 -> s2 -> ... -> sk such that: Every adjacent pair of words differs by a single letter. Every si for 1 <= i <= k is in wordList. Note that beginWord does not need to be in wordList. sk == endWord Given two words, beginWord and endWord, and a dictionary wordList, return the number of words in the shortest transformation sequence from beginWord to endWord, or 0 if no such sequence exists. ...