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?

Note: Given n will be a positive integer.

Example 1:

Input: 2
Output: 2
Explanation: There are two ways to climb to the top.
1. 1 step + 1 step
2. 2 steps
Example 2:

Input: 3
Output: 3
Explanation: There are three ways to climb to the top.
1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/climbing-stairs
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

 

 c =a +b;

斐波那契数列，可以递归，可以递推，也可以存在表里直接调，也可以整一个数组存

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