README.md

2373. Largest Local Values in a Matrix

You are given an n x n integer matrix grid.

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

• maxLocal[i][j] is equal to the largest value of the 3 x 3 matrix in grid centered around row i + 1 and column j + 1.

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:

• n == grid.length == grid[i].length
• 3 <= n <= 100
• 1 <= grid[i][j] <= 100

Solutions (Rust)

1. Solution

impl Solution {
    pub fn largest_local(grid: Vec<Vec<i32>>) -> Vec<Vec<i32>> {
        let n = grid.len();
        let mut max_local = vec![vec![0; n - 2]; n - 2];

        for i in 0..n - 2 {
            for j in 0..n - 2 {
                for a in 0..3 {
                    for b in 0..3 {
                        max_local[i][j] = max_local[i][j].max(grid[i + a][j + b]);
                    }
                }
            }
        }

        max_local
    }
}