백준 소스코드 [C++] 11598 1, 2, 3 더하기 3

www.acmicpc.net/problem/15988

15988번: 1, 2, 3 더하기 3

백준 소스코드 [C++] 11598 1, 2, 3 더하기 3

#include <iostream>
#include <algorithm>
#include <queue>
#include <string.h>
#include <limits.h>
#include <vector>
#include <math.h>
#include <stack>
#include <bitset>
#include <string>
typedef long long ll;
using namespace std;
ll arr[1000001];
void solve(int n) {
	if (arr[n] != 0) {
		cout << arr[n] << '\n';
		return;
	}
	else {
		for (int i = 4;i <= n;i++)
			if (arr[i] == 0)arr[i] = (arr[i - 1] + arr[i - 2] + arr[i - 3])%1000000009;
		cout << arr[n] << '\n';
		return;
	}
}
int main() {
	ios_base::sync_with_stdio(false), cin.tie(nullptr);
	int t, n;
	cin >> t;
	arr[1] = 1;
	arr[2] = 2;
	arr[3] = 4;
	while (t--) {
		cin >> n;
		solve(n);
	}
	
	return 0;
}