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：

这题本质上是斐波那契数列问题。这里采用数组暂存已有结果，以时间换空间，减少递归带来的重复计算。

代码实现：

class Solution {
public:
    int climbStairs(int n) {
        int f[n+1];
        f[0]=1;
        f[1]=1;
        
        for(int i=2;i<=n;++i){
            f[i]=f[i-1]+f[i-2];
        }
        return f[n];
    }
};