【Climbing Stairs】cpp

题目：

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?

代码：

class Solution {
public:
    int climbStairs(int n) {
        int prev = 0;
        int curr = 1;
        for (int i = 0; i<n; ++i)
        {
            const int tmp = curr;
            curr = curr + prev;
            prev = tmp;
        }
        return curr;
    }
};

Tips:

1. 这道题可以抽象成求Fibonacci数列的通项（只看最后一步：从n-1到n迈一个台阶；从n-2到n迈两个台阶）