Solution.go

func spiralOrder(matrix [][]int) (ans []int) {
	m, n := len(matrix), len(matrix[0])
	vis := make([][]bool, m)
	for i := range vis {
		vis[i] = make([]bool, n)
	}
	dirs := [5]int{0, 1, 0, -1, 0}
	i, j, k := 0, 0, 0
	for h := m * n; h > 0; h-- {
		ans = append(ans, matrix[i][j])
		vis[i][j] = true
		x, y := i+dirs[k], j+dirs[k+1]
		if x < 0 || x >= m || y < 0 || y >= n || vis[x][y] {
			k = (k + 1) % 4
		}
		i, j = i+dirs[k], j+dirs[k+1]
	}
	return
}