3242. Design Neighbor Sum Service

You are given a n x n 2D array grid containing distinct elements in the range [0, n2 - 1].

Implement the neighborSum class:

• neighborSum(int [][]grid) initializes the object.
• int adjacentSum(int value) returns the sum of elements which are adjacent neighbors of value, that is either to the top, left, right, or bottom of value in grid.
• int diagonalSum(int value) returns the sum of elements which are diagonal neighbors of value, that is either to the top-left, top-right, bottom-left, or bottom-right of value in grid.

3245. Alternating Groups III

There are some red and blue tiles arranged circularly. You are given an array of integers colors and a 2D integers array queries.

The color of tile i is represented by colors[i]:

• colors[i] == 0 means that tile i is red.
• colors[i] == 1 means that tile i is blue.

An alternating group is a contiguous subset of tiles in the circle with alternating colors (each tile in the group except the first and last one has a different color from its adjacent tiles in the group).

You have to process queries of two types:

• queries[i] = [1, sizei], determine the count of alternating groups with size sizei.
• queries[i] = [2, indexi, colori], change colors[indexi] to colori.

Return an array answer containing the results of the queries of the first type in order.

Note that since colors represents a circle, the first and the last tiles are considered to be next to each other.

3241. Time Taken to Mark All Nodes

There exists an undirected tree with n nodes numbered 0 to n - 1. You are given a 2D integer array edges of length n - 1, where edges[i] = [ui, vi] indicates that there is an edge between nodes ui and vi in the tree.

Initially, all nodes are unmarked. For each node i:

• If i is odd, the node will get marked at time x if there is at least one node adjacent to it which was marked at time x - 1.
• If i is even, the node will get marked at time x if there is at least one node adjacent to it which was marked at time x - 2.

Return an array times where times[i] is the time when all nodes get marked in the tree, if you mark node i at time t = 0.

Note that the answer for each times[i] is independent, i.e. when you mark node i all other nodes are unmarked.

3240. Minimum Number of Flips to Make Binary Grid Palindromic II

You are given an m x n binary matrix grid.

A row or column is considered palindromic if its values read the same forward and backward.

You can flip any number of cells in grid from 0 to 1, or from 1 to 0.

Return the minimum number of cells that need to be flipped to make all rows and columns palindromic, and the total number of 1‘s in grid divisible by 4.

3239. Minimum Number of Flips to Make Binary Grid Palindromic I

You are given an m x n binary matrix grid.

A row or column is considered palindromic if its values read the same forward and backward.

You can flip any number of cells in grid from 0 to 1, or from 1 to 0.

Return the minimum number of cells that need to be flipped to make either all rows palindromic or all columns palindromic.

3238. Find the Number of Winning Players

You are given an integer n representing the number of players in a game and a 2D array pick where pick[i] = [xi, yi] represents that the player xi picked a ball of color yi.

Player i wins the game if they pick strictly more than i balls of the same color. In other words,

• Player 0 wins if they pick any ball.
• Player 1 wins if they pick at least two balls of the same color.
• …
• Player i wins if they pick at leasti + 1 balls of the same color.

Return the number of players who win the game.

Note that multiple players can win the game.

1460. Make Two Arrays Equal by Reversing Subarrays

You are given two integer arrays of equal length target and arr. In one step, you can select any non-empty subarray of arr and reverse it. You are allowed to make any number of steps.

Return true if you can make arr equal to target or false otherwise.

Codeforces Round 910 (Div. 2) D. Absolute Beauty

Educational Codeforces Round 157 (Rated for Div. 2) D. XOR Construction

Codeforces Round 907 (Div. 2) D. Suspicious logarithms