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?

Solution: Climd one step from last stair or climb 2 steps from the last last stair.

class Solution {
public:
    int climbStairs(int n) {
        int last = 1;
        int lastlast = 1;
        for(int i = 2; i <= n; i++) {
            int step = last + lastlast;
            lastlast = last;
            last = step;
        }
        return last;
    }
};