package q54

import "math"

var dirs = [4][2]int{
	{1, 0},  // right
	{0, 1},  // down
	{-1, 0}, // left
	{0, -1}, // up
}

const VISITED = math.MinInt

func spiralOrder(matrix [][]int) []int {
	w, h := len(matrix[0]), len(matrix)
	cnt := w * h
	ret := make([]int, cnt)

	x, y := 0, 0
	dir := 0
	vect := dirs[dir]

	for i := range cnt {
		ret[i] = matrix[y][x]
		matrix[y][x] = VISITED

		// Can move?
		nextX, nextY := x+vect[0], y+vect[1]
		if nextX < 0 || nextY < 0 || nextX == w || nextY == h || matrix[nextY][nextX] == VISITED {
			dir = (dir + 1) % 4
			vect = dirs[dir]
			nextX, nextY = x+vect[0], y+vect[1]
		}
		x, y = nextX, nextY
	}

	return ret
}

var _ = spiralOrder