Submission #978044

#	Time	Username	Problem	Language	Result	Execution time	Memory
978044		VinhLuu	Kangaroo (CEOI16_kangaroo)	C++17	6 / 100	1 ms	2396 KiB

kangaroo

//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
#define int long long
//#define ll long long
#define fi first
#define se second
#define pb push_back
#define all(lmao) lmao.begin(), lmao.end()

using namespace std;

typedef pair<int,int> pii;
typedef tuple<int,int,int> tp;
const int N = 2e3 + 5;
const int oo = 1e9 + 1;
const int mod = 1e9 + 7;
//const ll oo = 5e18;

int n, a, b, f[N][N];

signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    #define task "v"
    if(fopen(task ".inp","r")){
        freopen(task ".inp","r",stdin);
        freopen(task ".out","w",stdout);
    }

    cin >> n >> a >> b;
    f[1][1] = 1;
    int cnt = 0;
    for(int i = 2; i <= n; i ++){
        for(int j = 1; j <= i; j ++){
            if(i == a || i == b){
                f[i][j] = (f[i - 1][j] + f[i - 1][j - 1]) % mod;
            }else{
                f[i][j] = (f[i - 1][j - 1] * (j -cnt) % mod + f[i - 1][j + 1] * j % mod) % mod;
            }
        }
        if(i == a || i == b) cnt++;
    }
    cout << f[n][1];

}

Compilation message (stderr)

kangaroo.cpp: In function 'int main()':
kangaroo.cpp:27:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   27 |         freopen(task ".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
kangaroo.cpp:28:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |         freopen(task ".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 0 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49