// Package q3567 implements a solution for https://leetcode.com/problems/minimum-absolute-difference-in-sliding-submatrix/
package q3567

import "slices"

var buf = make([]int, 30*30)

const INF = 1<<63 - 1

func minAbsDiffK(grid [][]int, xOffset, k int) int {
	if k == 1 {
		return 0
	}

	numbers := buf[:0]
	for y := range k {
		for x := range k {
			numbers = append(numbers, grid[y][x+xOffset])
		}
	}
	slices.Sort(numbers)
	minDiff := INF
	for i := 1; i < len(numbers); i++ {
		if numbers[i] == numbers[i-1] {
			continue
		}
		minDiff = min(minDiff, numbers[i]-numbers[i-1])
	}
	if minDiff == INF {
		return 0
	}
	return minDiff
}

func minAbsDiff(grid [][]int, k int) [][]int {
	w, h := len(grid[0]), len(grid)
	for i := 0; i < h-k+1; i++ {
		for j := 0; j < w-k+1; j++ {
			grid[i][j] = minAbsDiffK(grid[i:], j, k)
		}
	}
	for i := range h - k + 1 {
		grid[i] = grid[i][:w-k+1]
	}
	return grid[:h-k+1]
}

var _ = minAbsDiff