Climbing Stairs

【题目描述】

You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

【思路】

数学题。找到规律即可。当n=1，ways(1)=1,当n=2，ways(2)=2,当n>=3时，ways(n)=ways(n-1)+ways(n-2)

【代码】

class Solution {public:    int climbStairs(int n) {        int ans;        int one=1;        int two=2;        if(n==1) return 1;        if(n==2) return 2;        for(int i=3;i<=n;i++){            ans=one+two;            one=two;            two=ans;        }        return ans;    }};