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?

Have you met this question in a real interview? Yes
Example
Given an example n=3 , 1+1+1=2+1=1+2=3

return 3

 

public int climbStairs(int n) {
       
        if (n <= 1) {
            return 1;
        }
        int last = 1, lastlast = 1;
        int now = 0;
        for (int i = 2; i <= n; i++) {
            now = last + lastlast;
            lastlast = last;
            last = now;
        }
        
        return now;
}