LeetCode in Kotlin

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:

• 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

Solution

class Solution {
    fun largestLocal(grid: Array<IntArray>): Array<IntArray> {
        val n = grid.size
        val res = Array(n - 2) { IntArray(n - 2) }
        for (i in 0 until n - 2) {
            for (j in 0 until n - 2) {
                for (p in i until i + 3) {
                    for (q in j until j + 3) {
                        res[i][j] = Math.max(res[i][j], grid[p][q])
                    }
                }
            }
        }
        return res
    }
}

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