[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?

思考：DP，斐波拉契。

class Solution {
public:
    int climbStairs(int n) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
		if(n<=2) return n;
		int a=1,b=2,c;
		for(int i=3;i<=n;i++)
		{
			c=a+b;
			a=b;
			b=c;
		}
		return c;
    }
};