Cod sursa(job #442316)

Utilizator alexandru92alexandru alexandru92 Data 14 aprilie 2010 09:14:35
Problema Flux maxim Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.56 kb
#include <queue>
#include <cstdlib>
#include <fstream>
#define Nmax 1001
#define SIZE 8219

/*
 *
 */
using namespace std;
ifstream in;
int ifile;
char file[SIZE];
int C[Nmax][Nmax];
vector< int > f, d;
vector< vector< int > > G;
vector< int >::const_iterator it, iend;
inline void read( int& x )
{
	x=0;
	while( file[ifile] < '0' || file[ifile] > '9' )
		if( ++ifile == SIZE )
		{
			in.read( file, SIZE );
			ifile=0;
		}
	while( file[ifile] >= '0' && file[ifile] <= '9' )
	{
		x=x*10+file[ifile]-'0';
		if( ++ifile == SIZE )
		{
			in.read( file, SIZE );
			ifile=0;
		}
	}
}
inline int find_path( void )
{
	int x, N=f.size();
	queue< int > Q;
	f.assign( N, -1 );
	f[0]=-2;
	d[0]=0x3f3f3f3f;
	for( Q.push(0), N-=1; -1 == f[N] && !Q.empty(); )
	{
		x=Q.front(); Q.pop();
		for( it=G[x].begin(), iend=G[x].end(); it < iend; ++it )
			if( -1 == f[*it] && C[x][*it] > 0 )
			{
				f[*it]=x;
				d[*it]=min( d[x], C[x][*it] );
				Q.push(*it);
			}
	}
	if( -1 == f[N] )
		return 0;
	for( x=N; -2  != f[x]; x=f[x] )
	{
		C[x][f[x]]+=d[N];
		C[f[x]][x]-=d[N];
	}
	return d[N];
}
inline int MaximumFlow( void )
{
	int s, p;
	for( s=0, p=find_path(); p; s+=p, p=find_path() );
	return s;
}
int main( void )
{
	int N, M, x, y;
	in.open( "maxflow.in" );
	read(N); read(M);
	G.resize(N);
	f.resize(N);
	d.resize(N);
	for( ; M; --M )
	{
		read(x); read(y);
		--x, --y;
		read( C[x][y] );
		G[x].push_back(y);
		G[y].push_back(x);
	}
	ofstream out( "maxflow.out" );
	out<<MaximumFlow()<<'\n';
	return EXIT_SUCCESS;
}