70. Climbing Stairs

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?

用动态规划做，然后发现其实就是斐波那契数列。

代码：

class Solution {
public:
    int climbStairs(int n) {
        if(n==0) return 0;
        if(n==1) return 1;
        vector<int>res(n+1);
        res[1]=1;res[2]=2;
        for(int i=3;i<=n;i++)
        {
            res[i]=res[i-1]+res[i-2];
        }
        return res[n];
    }
};