ClimbStairs 1 or 2 at a time

class Solution {

    public int climbStairs( int n) {
        int[] memo = new int[n+1];
        memo[0] = 1;
        memo[1] = 1;
        for(int i = 2; i<=n; i++){
            memo[i] = memo[i-2] + memo[i-1];
        }
        return memo[n];
    }
}