LeetCode：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?

// Source : https://oj.leetcode.com/problems/climbing-stairs/// Author : Chao Zeng// Date   : 2014-12-20class Solution {public:    int climbStairs(int n) {        if (n == 1)            return 1;        if (n == 2)            return 2;        int first = 0;        int second = 1;        int ans = 2;        for (int i = 3; i <= n; i++){                first = second;                second = ans;                ans = first + second;        }        return ans;    }};