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?

class Solution {
public:
    int climbStairs(int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int dp1 = 1, dp2 = 2,dp;
        dp = n == 1 ? dp1 : dp2;
        for(int i = 3; i <= n; i++){
            dp = dp1 + dp2;
            dp1 = dp2;
            dp2 = dp;
        }
        return dp;
    }
};