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?

 

解题思路：

斐波那契。。。

class Solution { public:     int climbStairs(int n) {         if(n<=2)return n;         int a=1,b=2;         for(int i=3;i<=n;i++){             int tmp=a+b;             a=b;             b=tmp;         }         return b;     } };