LeetCode70 - Climbing Stairs--爬楼梯，斐波那契数列

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?

Note: Given n will be a positive integer.

思路：到第ｎ个台阶的迈法种数＝到第ｎ－１个台阶的迈法种数（再往上迈一步）＋到第ｎ－２个台阶的迈法种数（再往上迈两步）。斐波那契数列的问题。

class Solution {
public:
    int climbStairs(int n) 
    {
        int f1=0;
        int f2=1;
        int sum=0;
        for(int i=0;i<n;i++)
        {
            sum=f1+f2;
            f1=f2;
            f2=sum;
        }
        return sum;   
    }
};