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?

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

class Solution {
public:
    int climbStairs(int n) {
        int a=0,b=0,c=1;
        //动态规划，1时为1，2时为2，f(x) =f(x-1)+f(x-2);
        //滑动数组
        for(int i=0;i<n;i++)
        {
            a=b;
            b=c;
            c=a+b;
        }
        return c;
    }
};

注意：深度搜索的话，重复的子集太多，应该采用动态规划。