Number of Ways to Paint N × 3 Grid LeetCode solution in C++

1
class Solution {
2
 public:
3
  int numOfWays(int n) {
4
    int mod = 1e9 + 7;
5
    long long c2 = 6, c3 = 6;
6
    for (int i = 2; i <= n; i++) {
7
      long long temp = c3;
8
      c3 = (2 * c3 + 2 * c2) % mod;
9
      c2 = (2 * temp + 3 * c2) % mod;
10
    }
11
    return (c2 + c3) % mod;
12
  }
13
};