Submission #696550

#	Time	Username	Problem	Language	Result	Execution time	Memory
696550		lucri	Ruins 3 (JOI20_ruins3)	C++17	100 / 100	1399 ms	7624 KiB

ruins3

#include <bits/stdc++.h>
#define MOD  1000000007
using namespace std;
long long putere(long long a,long long b)
{
    if(b==0)
        return 1;
    long long p=putere(a,b/2);
    p*=p;
    p%=MOD;
    if(b%2)
    {
        p*=a;
        p%=MOD;
    }
    return p;
}
int fact[610],comb[610][610];
void factorial()
{
    fact[0]=1;
    for(long long i=1;i<=600;++i)
        fact[i]=fact[i-1]*i%MOD;
}
long long combinari(long long n,long long m)
{
    long long ans=1;
    ans=fact[n];
    ans*=putere(fact[m],MOD-2);
    ans%=MOD;
    ans*=putere(fact[n-m],MOD-2);
    ans%=MOD;
    return ans;
}
long long n,v[610],ans[610][610][2],cans[610][610][2];
long long raspunde(short step,short nrstack,short ppoz,bool exista)
{
    int vans=0;
    short ramas=n-step-nrstack;
    short posibileInceput=v[ppoz]-1-(2*step-step+ppoz-1-nrstack);
    if(posibileInceput<0||ramas<0||ramas==0&&exista==false||nrstack==0&&exista==true)
        return 0;
    if(exista==false)
    {
        if(ramas>=3)
            vans=(1LL*vans+1LL*comb[ramas-1][2]*cans[nrstack+1][ppoz][false])%MOD;
        if(ramas>=2)
            vans=(1LL*vans+1LL*(ramas-1)*cans[nrstack+1][ppoz][true])%MOD;
        if(posibileInceput>=2&&nrstack>=1)
            vans=(1LL*vans+1LL*comb[posibileInceput][2]*cans[nrstack-1][ppoz][false])%MOD;
        if(posibileInceput&&nrstack>=1&&ramas>=1)
        {
            if(ramas-1)
                vans=(1LL*vans+1LL*posibileInceput*(ramas-1)%MOD*cans[nrstack][ppoz][false])%MOD;
            vans=(1LL*vans+1LL*posibileInceput*cans[nrstack][ppoz][true])%MOD;
        }
        else if(posibileInceput&&ramas>=1)
        {
            if(step==n-1)
                return 1;
            if(ramas-1)
                vans=(1LL*vans+1LL*posibileInceput*(ramas-1)%MOD*cans[nrstack][ppoz][false])%MOD;
            int q=putere(comb[n-ppoz][step+1-ppoz],MOD-2);
            for(int newppoz=ppoz+1;newppoz<=step+2;++newppoz)
                vans=(1LL*vans+1LL*comb[n-newppoz][step+2-newppoz]*q%MOD*posibileInceput%MOD*cans[nrstack][newppoz][false])%MOD;
        }
    }
    else
    {
        if(ramas>=2)
            vans=(1LL*vans+1LL*comb[ramas][2]*cans[nrstack+1][ppoz][true])%MOD;
        if(posibileInceput>=2)
        {
            if(nrstack>=2)
                vans=(1LL*vans+1LL*comb[posibileInceput][2]*cans[nrstack-1][ppoz][true])%MOD;
            else
            {
                if(step==n-1)
                    return 1;
                int q=putere(comb[n-ppoz][step+1-ppoz],MOD-2);
                for(int newppoz=ppoz+1;newppoz<=step+2;++newppoz)
                    vans=(1LL*vans+1LL*comb[n-newppoz][step+2-newppoz]*q%MOD*comb[posibileInceput][2]%MOD*cans[nrstack-1][newppoz][false])%MOD;
            }
        }
        if(posibileInceput&&ramas>=1)
            vans=(1LL*vans+1LL*posibileInceput*ramas%MOD*cans[nrstack][ppoz][true])%MOD;
    }
    return vans;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    factorial();
    cin>>n;
    for(int i=1;i<=n;++i)
        cin>>v[i];
    for(int i=0;i<=n;++i)
        for(int j=0;j<=i;++j)
            comb[i][j]=combinari(i,j);
    for(int step=n-1;step>=0;--step)
    {
        for(int nrstack=0;nrstack<=step&&nrstack+step<=n;++nrstack)
            for(int ppoz=1;ppoz<=step+1;++ppoz)
                for(int q=0;q<=1;++q)
                    ans[nrstack][ppoz][q]=raspunde(step,nrstack,ppoz,q);
        for(int nrstack=0;nrstack<=step&&nrstack+step<=n;++nrstack)
            for(int ppoz=1;ppoz<=step+1;++ppoz)
                for(int q=0;q<=1;++q)
                    cans[nrstack][ppoz][q]=ans[nrstack][ppoz][q];
    }
    cout<<ans[0][1][false];
    return 0;
}

Compilation message (stderr)

ruins3.cpp: In function 'long long int raspunde(short int, short int, short int, bool)':
ruins3.cpp:41:44: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   41 |     if(posibileInceput<0||ramas<0||ramas==0&&exista==false||nrstack==0&&exista==true)
      |                                    ~~~~~~~~^~~~~~~~~~~~~~~
ruins3.cpp:41:71: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   41 |     if(posibileInceput<0||ramas<0||ramas==0&&exista==false||nrstack==0&&exista==true)
      |                                                             ~~~~~~~~~~^~~~~~~~~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 52 / 52
• Subtask 3: 42 / 42