Submission #745235

#	Time	Username	Problem	Language	Result	Execution time	Memory
745235		Ahmed57	Magneti (COCI21_magneti)	C++17	10 / 110	27 ms	1876 KiB

Main

#include <iostream>

using namespace std;

#define mod 1000000007

long long fact[100001],inverse[100001];

long long power(long long x,long long n)
{
    if (n == 0) {
        return 1;
    }
    long long pow = power(x, n / 2)%mod;
    if (n & 1) {
        return ((((x%mod) * (pow%mod))%mod) * pow%mod)%mod;
    }
    return ((pow%mod) * (pow%mod))%mod;
}

long long solve(int a,int b){
    return((fact[a]*inverse[b])%mod*inverse[a-b])%mod;
}
long long stars(long long a,long long b){
    return solve(a+b-b,b);
}
int main()
{
    fact[0] = inverse[0] = fact[1] = inverse[1] = 1;
    for(int i = 2;i<=1e5;i++){
        fact[i]=fact[i-1]*i;
        fact[i]%=mod;
        inverse[i] = power(fact[i],mod-2);
    }
    long long n,l,x;
    cin>>n>>l;
    for(int i = 0;i<n;i++){
        cin>>x;
    }
    if(l<(n-1)*x){
        cout<<0<<endl;
        return 0;
    }
    cout<<(stars(l-(n-1)*(x-1),n)*fact[n])%mod<<endl;
    return 0;
}

• Subtask 1: 10 / 10
• Subtask 2: 0 / 20
• Subtask 3: 0 / 30
• Subtask 4: 0 / 50