"sort"

	log.Println(solveSecond(matrix))

type Seen map[[2]int]bool
func solveSecond(m Matrix) int {
	lows := m.getLows()

	var ret = make([]int, len(lows))
	var seen = Seen{}
	for i, item := range lows {
		ret[i] = seen.getBasinSize(m, item)
	}
	sort.Ints(ret)
	return ret[len(ret)-1] * ret[len(ret)-2] * ret[len(ret)-3]
}
func (seen Seen) getBasinSize(m Matrix, item [2]int) int {
	var ret int
	row, col := item[0], item[1]
	if seen[item] || m[row][col] == 9 {
		return 0
	}
	seen[item] = true
	ret++
	for _, d := range directions {
		if row+d[0] >= 0 && row+d[0] < len(m) &&
			col+d[1] >= 0 && col+d[1] < len(m[0]) {
			if m[row+d[0]][col+d[1]] != 9 {
				ret += seen.getBasinSize(m, [2]int{row + d[0], col + d[1]})
			}
		}
	}
	return ret
}
func (m Matrix) getLows() [][2]int {
	var ret [][2]int
	for row, line := range m {
		for col := range line {
			if m.checkLow(row, col) {
				ret = append(ret, [2]int{row, col})
			}
		}
	}
	return ret
}