70. 爬楼梯
https://leetcode-cn.com/problems/climbing-stairs/
这题和上一题 509. 斐波那契数 解题方法是一样的,都是递推
func climbStairs(n int) int {
if n < 3 {
return n
}
q, w, r := 0, 1, 2
for i := 2; i < n; i++ {
q = w
w = r
r = q + w
}
return r
}