70. Climbing Stairs

public class Solution {
    public int climbStairs(int n) {
        if(n==1)
            return 1;
        if(n==2)
            return 2;
        int[] res=new int[n+1];
        res[1]=1;
        res[2]=2;
        for(int i=3;i<=n;i++)
        {
            int temp=res[i-1]+res[i-2];
            res[i]=temp;
        }
        return res[n];
    }
}