leetcode[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?

class Solution {

public:

    int climbStairs(int n) {

        if(n<=2)return n;

        int *s=new int[n];

        s[0]=1;

        s[1]=2;

        for(int i=2;i<n;i++)

        {

            s[i]=s[i-1]+s[i-2];

        }

        return s[n-1];

    }

};