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?

Note: Given n will be a positive integer.

Approach : The standard recursive solution times out so the idea is to use the iterative solution to find the nth fibonacci number.

int climbStairs(int n) {
    int f1 = 2;
    int f2 = 1;
    if(n == 1) {
        return f2;
    } else if(n == 2) {
        return f1;
    }

    int fn;
    for(int i = 3; i <= n; i++) {
        fn = f1 + f2;
        f2 = f1;
        f1 = fn;
    }
    return fn;
}

Here is the link to the ideone solution : http://ideone.com/ErEU6E