340. 걷다보니 신천역 삼 (Small)

백준

참고

1. Python

2. C++

#include <iostream>
#define n_ 2200
using namespace std;

int n;

int solve(int sum, int t) {
	if (t == n)
		return sum % 3 ? 0 : 1;

	int ret = 0;
	ret += solve(sum + 0, t + 1);
	ret += solve(sum + 1, t + 1);
	ret += solve(sum + 2, t + 1);
	return ret;
}

int main(void) {
	cin >> n;

	int res = 0;
	res += solve(1, 1);
	res += solve(2, 1);
	cout << res << endl;

	return 0;
}