// Package q3643 implements a solution for https://leetcode.com/problems/flip-square-submatrix-vertically/
package q3643

func reverseSubmatrix(grid [][]int, x int, y int, k int) [][]int {
	x, y = y, x // lol
	swapBuf := make([]int, k)

	for i := range k / 2 {
		y1 := y + i
		y2 := y + k - 1 - i

		copy(swapBuf, grid[y1][x:x+k])
		copy(grid[y1][x:x+k], grid[y2][x:x+k])
		copy(grid[y2][x:x+k], swapBuf)
	}
	return grid
}

var _ = reverseSubmatrix