Cod sursa(job #984330)

Utilizator AlexandruValeanuAlexandru Valeanu AlexandruValeanu Data 14 august 2013 10:06:11
Problema Flux maxim Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 2.25 kb
#include <iostream>
#include <fstream>
#include <vector>
#include <cstring>

using namespace std;

#define Nmax 1003
#define INF 0x3f3f3f3f

vector <int> G[Nmax];
int coada[Nmax];
int viz[Nmax];
int tata[Nmax];
int F[Nmax][Nmax];
int C[Nmax][Nmax];

int N, M;

void read()
{
    ifstream f("maxflow.in");

    f >> N >> M;

    for ( int i = 1, a, b, c; i <= M; ++i )
    {
        f >> a >> b >> c;

        C[a][b] = c;

        G[a].push_back( b );
        G[b].push_back( a );
    }

    f.close();
}

inline bool BFS( int sourse, int destination )
{
    memset( viz, 0, sizeof( viz ) );

    int st, dr;

    coada[st = dr = 1] = sourse;
    viz[sourse] = 1;

    for (; st <= dr; )
    {
        int nod = coada[ st++ ];

        for ( unsigned i = 0; i < G[nod].size(); ++i )
        {
            int vertex = G[nod][i];

            if ( !viz[vertex] && C[nod][vertex] > F[nod][vertex] )
            {
                tata[vertex] = nod;
                viz[vertex] = 1;

                coada[ ++dr ] = vertex;

                if ( vertex == destination )
                        return true;
            }
        }
    }

    return false;
}

int Edmonds_Karp( int sourse, int destination )
{
    int flow = 0, fmin, nod;

    while( BFS( sourse, destination ) )
    {
        for ( unsigned i = 0; i < G[destination].size(); ++i )
        {
            int son = G[destination][i];

            if ( !viz[son] || F[son][destination] >= C[son][destination] )
                    continue;

            fmin = INF;
            tata[destination] = son;

            for ( nod = destination; nod != sourse; nod = tata[nod] )
                    fmin = min( fmin, C[ tata[nod] ][nod] - F[ tata[nod] ][nod] );

            if ( !fmin )
                    continue;

            for ( nod = destination; nod != sourse; nod = tata[nod] )
            {
                F[ tata[nod] ][nod] += fmin;
                F[nod][ tata[nod] ] -= fmin;
            }

            flow += fmin;
        }
    }

    return flow;
}

void print()
{
    ofstream g("maxflow.out");

    g << Edmonds_Karp( 1, N ) << "\n";

    g.close();
}

int main()
{
    read();
    print();

    return 0;
}