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.

LeetCode Problem - 2373

class Solution {

    // Method to find the largest local values in a given grid
    public int[][] largestLocal(int[][] grid) {
        // The length of the new array will be 2 less than the length of the grid
        int outerLoopIteration = grid.length - 2;

        // Initialize a new array to store the largest local values
        int[][] newArray = new int[outerLoopIteration][outerLoopIteration];

        // Iterate over each element of the new array
        for(int i = 0; i < newArray.length; i++){
            for(int j = 0; j < newArray.length; j++){
                // Find the largest element in the 3x3 subgrid and assign it to the new array
                newArray[i][j] = findLargerElement(grid, i, j);
            }
        }
        // Return the new array containing the largest local values
        return newArray;
    }

    // Helper method to find the largest element in a 3x3 subgrid
    public int findLargerElement(int[][] grid, int row, int col){
        // Initialize the maximum value to the smallest possible integer
        int maxValue = Integer.MIN_VALUE;

        // Iterate over each element in the 3x3 subgrid
        for (int i = row; i < row + 3; i++){
            for (int j = col; j < col + 3; j++){
                // Update the maximum value if a larger element is found
                if (grid[i][j] > maxValue){
                    maxValue = grid[i][j];
                }
            }
        }
        // Return the largest element found in the 3x3 subgrid
        return maxValue;
    }
}