백준 15990번 1, 2, 3 더하기 5 C++

https://www.acmicpc.net/problem/15990

15990번: 1, 2, 3 더하기 5

 

다이나믹 프로그래밍

 

#include <iostream>
#include <string>
#include <vector>
#include <math.h>
#include <algorithm>
#include <utility>
#include <stack>
#include <queue>
#include <math.h>
#include <set>
#include <map>
#include <list>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <limits.h>

using namespace std;
using int64 = long long;

const int64 mod = 1000000009;
vector<vector<int64>> cache;

int64 dp(int n, int lastN) {
    if (n <= 0) return 0;
    int64& val = cache[n][lastN];
    if (val != -1) return val;
    val = 0;
    for (int i = 1; i <= 3; i++) {
        if (lastN == i) continue;
        val += dp(n - lastN, i);
    }
    val %= mod;
    return val;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    int t;
    cin >> t;
    cache = vector<vector<int64>>(100001, vector<int64>(4, -1));
    cache[1][1] = 1;
    cache[2][2] = 1;
    cache[3][1] = 1;
    cache[3][2] = 1;
    cache[3][3] = 1;

    while (t--) {
        int n;
        cin >> n;
        int64 ans = dp(n, 1) + dp(n, 2) + dp(n, 3);
        ans %= mod;
        cout << ans << "\n";
    }
}