Largest local values in a matrix

Array Matrix

87.7% acceptance

Feb 25, 2026

1320

182

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.

Solution

Rust

Time O(n²)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn largest_local(grid: Vec<Vec<i32>>) -> Vec<Vec<i32>> {
    let n = grid.len();
    (0..n-2).map(|i| {
      (0..n-2).map(|j| {
        let mut mx = 0;
        for di in 0..3 { for dj in 0..3 { mx = mx.max(grid[i+di][j+dj]); } }
        mx
      }).collect()
    }).collect()
  }
}