package q70

func nWays(n, i int, cache []int) int {
	if i == n {
		return 1
	}
	if i > n {
		return 0
	}
	if cache == nil {
		cache = make([]int, n)
	} else if cache[i] != 0 {
		return cache[i]
	}
	ret := nWays(n, i+1, cache) + nWays(n, i+2, cache)
	cache[i] = ret
	return ret
}

func climbStairs(n int) int {
	return nWays(n, 0, nil)
}

var _ = climbStairs