Cod sursa(job #551144)

Utilizator BitOneSAlexandru BitOne Data 10 martie 2011 13:49:16
Problema Flux maxim Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 1.42 kb
#include <queue>
#include <vector>
#include <fstream>
#include <cstdlib>
#define N_MAX 1011
#define oo 1<<20

using namespace std;
int N;
vector< int > f;
int C[N_MAX][N_MAX], F[N_MAX][N_MAX];
vector< int > G[N_MAX];
inline int _min( int x, int y ) { return ( x <= y ? x : y ); }
bool findPath()
{
	int x;
	queue< int > Q;
	vector< int >::const_iterator it, iend;
	f.assign( N+1, -1 );
	f[1]=-2;
	for( Q.push(1); !Q.empty(); )
	{
		x=Q.front(); Q.pop();
		if( N == x )
			continue;
		for( it=G[x].begin(), iend=G[x].end(); it < iend; ++it )
			if( -1 == f[*it] && C[x][*it] > F[x][*it] )
			{
				f[*it]=x;
				Q.push(*it);
			}		
	}
	if( -1 == f[N] )
		return false;
	return true;
}
int MaxFlow()
{
	int min, x, s;
	vector< int >::const_iterator it, iend;
	for( s=0; findPath(); )
	{
		for( it=G[N].begin(), iend=G[N].end(); it < iend; ++it )
			if( -1 != f[*it] && C[*it][N] > F[*it][N] )
			{
				f[N]=*it;
				min=oo;
				for( x=N; -2 != f[x]; x=f[x] )
					min=_min( min, C[f[x]][x]-F[f[x]][x] );
				for( x=N; -2 != f[x]; x=f[x] )
				{
					F[f[x]][x]+=min;
					F[x][f[x]]-=min;
				}
				s+=min;
			}
	}
	return s;
}
int main( void )
{
	int M, x, y;
	ifstream in( "maxflow.in" );
	for( in>>N>>M; M; --M )
	{
		in>>x>>y;
		in>>C[x][y];
		G[x].push_back(y);
		G[y].push_back(x);
	}
	f.resize( N+1 );
	ofstream out( "maxflow.out" );
	out<<MaxFlow()<<'\n';
	return EXIT_SUCCESS;
}