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?public class Solution {
public int climbStairs(int n) {
if(n==1) return 1;
int[] res = new int[2];
res[0] = 1;
res[1] = 2;
while(n>2){
int t = res[1];
res[1] += res[0];
res[0] = t;
n--;
}
return res[1];
}
}