Climbing Stairs

Description:

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?

Code:

    int climbStairs(int n) {

        if (1==n)

            return 1;

        else if (2==n)

            return 2;

        else

        {

            int p = 1, q = 2, result = 0;

            for (int i = 3; i <= n; i++)

            {

                result = p + q;

                 p = q;

                q = result;

            }

            return result;

        }

    }