leetcode 70 爬楼梯

 1 class Solution {
 2 public:
 3     int climbStairs(int n) {
 4         int res=1,i=1;
 5         while(n>1){
 6             n=n-2;
 7             int m=n+i;
 8             int temp=tm(m)/(tm(i)*tm(m-i));
 9             res+=temp;
10             i++;
11         }
12         return res;
13     }
14     int tm(int n){
15         if(n==0) return 1;
16         return n*tm(n-1);
17     }
18 };

class Solution(object):
    def climbStairs(self, n):
        """
        :type n: int
        :rtype: int
        """
        #空间复杂度2，时间复杂度n
        a=0
        b=1
        for i in range(n):
            a,b=b,a+b
        return b