LeetCode in Kotlin

3567. Minimum Absolute Difference in Sliding Submatrix

Medium

You are given an m x n integer matrix grid and an integer k.

For every contiguous k x k submatrix of grid, compute the minimum absolute difference between any two distinct values within that submatrix.

Return a 2D array ans of size (m - k + 1) x (n - k + 1), where ans[i][j] is the minimum absolute difference in the submatrix whose top-left corner is (i, j) in grid.

Note: If all elements in the submatrix have the same value, the answer will be 0.

A submatrix (x1, y1, x2, y2) is a matrix that is formed by choosing all cells matrix[x][y] where x1 <= x <= x2 and y1 <= y <= y2.

Example 1:

Input: grid = [[1,8],[3,-2]], k = 2

Output: [[2]]

Explanation:

• There is only one possible k x k submatrix: [[1, 8], [3, -2]].
• Distinct values in the submatrix are [1, 8, 3, -2].
• The minimum absolute difference in the submatrix is |1 - 3| = 2. Thus, the answer is [[2]].

Example 2:

Input: grid = [[3,-1]], k = 1

Output: [[0,0]]

Explanation:

• Both k x k submatrix has only one distinct element.
• Thus, the answer is [[0, 0]].

Example 3:

Input: grid = [[1,-2,3],[2,3,5]], k = 2

Output: [[1,2]]

Explanation:

• There are two possible k × k submatrix:
  • Starting at (0, 0): [[1, -2], [2, 3]].
    • Distinct values in the submatrix are [1, -2, 2, 3].
    • The minimum absolute difference in the submatrix is |1 - 2| = 1.
  • Starting at (0, 1): [[-2, 3], [3, 5]].
    • Distinct values in the submatrix are [-2, 3, 5].
    • The minimum absolute difference in the submatrix is |3 - 5| = 2.
• Thus, the answer is [[1, 2]].

Constraints:

• 1 <= m == grid.length <= 30
• 1 <= n == grid[i].length <= 30
• -105 <= grid[i][j] <= 105
• 1 <= k <= min(m, n)

Solution

import kotlin.math.min

class Solution {
    fun minAbsDiff(grid: Array<IntArray>, k: Int): Array<IntArray> {
        val rows = grid.size
        val cols = grid[0].size
        val result = Array<IntArray>(rows - k + 1) { IntArray(cols - k + 1) }
        for (x in 0..rows - k) {
            for (y in 0..cols - k) {
                val size = k * k
                val elements = IntArray(size)
                var idx = 0
                for (i in x..<x + k) {
                    for (j in y..<y + k) {
                        elements[idx++] = grid[i][j]
                    }
                }
                elements.sort()
                var minDiff = Int.Companion.MAX_VALUE
                for (i in 1..<size) {
                    if (elements[i] != elements[i - 1]) {
                        minDiff = min(minDiff, elements[i] - elements[i - 1])
                        if (minDiff == 1) {
                            break
                        }
                    }
                }
                result[x][y] = if (minDiff == Int.Companion.MAX_VALUE) 0 else minDiff
            }
        }
        return result
    }
}

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