← All problems

2373. Largest Local Values in a Matrix

EasyOpen on LeetCodeProblem statement

Problem Statement

2373. Largest Local Values in a Matrix

Easy

You are given an n x n integer matrix grid.

Generate an integer matrix maxLocal of size (n - 2) x (n - 2) such that:

In other words, we want to find the largest value in every contiguous 3 x 3 matrix in grid.

Return the generated matrix.

 

Example 1:

Input: grid = [[9,9,8,1],[5,6,2,6],[8,2,6,4],[6,2,2,2]]
Output: [[9,9],[8,6]]
Explanation: The diagram above shows the original matrix and the generated matrix.
Notice that each value in the generated matrix corresponds to the largest value of a contiguous 3 x 3 matrix in grid.

Example 2:

Input: grid = [[1,1,1,1,1],[1,1,1,1,1],[1,1,2,1,1],[1,1,1,1,1],[1,1,1,1,1]]
Output: [[2,2,2],[2,2,2],[2,2,2]]
Explanation: Notice that the 2 is contained within every contiguous 3 x 3 matrix in grid.

 

Constraints:

Java

Source file
class Solution {
    public int solve(int[][] grid, int x, int y){
        int maxLocal = 0;
        for(int i=x-1; i<=x+1; i++)
            for(int j=y-1; j<=y+1; j++)
                maxLocal = Math.max(maxLocal, grid[i][j]);
        return maxLocal;
    }
    public int[][] largestLocal(int[][] grid) {
        int k = grid.length-2;
        int[][] ans = new int[k][k];
        for(int i=0; i<k; i++)
            for(int j=0; j<k; j++)
                ans[i][j] = solve(grid, i+1, j+1);
        return ans;
    }
}