Submission #399612

#	Time	Username	Problem	Language	Result	Execution time	Memory
399612		KienTranluvChaeng	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	53 ms	31708 KiB

kangaroo

#include <bits/stdc++.h>
#define int long long
#define mod 1000000007

using namespace std;

void Add(int &x, int y){
    x += y; x %= mod;
}

main(){
    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int n, cs, cf; cin >> n >> cs >> cf;
    vector <int> f[n + 2];
    for (int i = 1; i <= n; ++ i) f[i].resize(n + 2);
    f[1][0] = 1;
    for (int i = 1; i < n; ++ i){
        for (int j = 0; j <= i; ++ j){
            if (i == cs || i == cf){
                Add(f[i + 1][j], f[i][j]);
                if (j) Add(f[i + 1][j - 1], f[i][j] * j);
                continue;
            }
            Add(f[i + 1][j + 1], f[i][j]);
            if (j) Add(f[i + 1][j - 1], f[i][j] * j % mod * (j - 1) % mod);
            if (i > cs && j) Add(f[i + 1][j - 1], j * f[i][j]);
            if (i > cf && j) Add(f[i + 1][j - 1], j * f[i][j]);
        }
    }
    cout << f[n][0];
}

Compilation message (stderr)

kangaroo.cpp:11:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   11 | main(){
      |      ^

• Subtask 1: 6 / 6
• Subtask 2: 30 / 30
• Subtask 3: 15 / 15
• Subtask 4: 49 / 49