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?

很明显看出这是个斐波那契数列，但是我们一般不用递归的方法，而采用循环来求解

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

LeetCode 70. Climbing Stairs