Submission #704072

#	Time	Username	Problem	Language	Result	Execution time	Memory
704072		Pacybwoah	Magneti (COCI21_magneti)	C++14	110 / 110	201 ms	208456 KiB

Main

#include<iostream>
#include<vector>
#include<algorithm>
#define ll long long
using namespace std;
const ll mod=1e9+7;
ll power(ll a,ll b){
    if(b==0) return 1;
    if(b&1) return power(a,b-1)*a%mod;
    ll tmp=power(a,b/2);
    return tmp*tmp%mod;
}
ll inverse(ll a){
    return power(a,mod-2);
}
int main(){
    ll n,l;
    cin>>n>>l;
    vector<ll> vec(n);
    vector<ll> fac(20001);
    fac[0]=1;
    for(ll i=1;i<=20000;i++) fac[i]=fac[i-1]*i%mod;
    vector<ll> invfac(20001);
    for(ll i=0;i<=20000;i++) invfac[i]=inverse(fac[i]);
    for(int i=0;i<n;i++) cin>>vec[i];
    vector<vector<vector<ll>>> dp(n+1,vector<vector<ll>>(n+1,vector<ll>(l+1,0)));
    dp[1][1][0]=1;
    sort(vec.begin(),vec.end());
    for(ll i=2;i<=n;i++){
        for(ll j=1;j<=i;j++){
            for(ll k=0;k<=l;k++){
                if(j+1<=n&&k-2*vec[i-1]>=0) dp[i][j][k]=dp[i-1][j+1][k-2*vec[i-1]]*(j*(j+1)%mod)%mod;
                if(j-1>=0) dp[i][j][k]=(dp[i][j][k]+dp[i-1][j-1][k])%mod;
                if(k-vec[i-1]>=0) dp[i][j][k]=(dp[i][j][k]+dp[i-1][j][k-vec[i-1]]*j*2%mod)%mod;
            }
        }
    }
    ll ans=0;
    for(int i=0;i<l;i++){
        ans=(ans+fac[l-1-i+n]*invfac[n]%mod*invfac[l-1-i]%mod*dp[n][1][i]%mod)%mod;
    }
    cout<<ans;
}

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