Cod sursa(job #1152092)

Utilizator ThomasFMI Suditu Thomas Thomas Data 24 martie 2014 15:42:53
Problema Flux maxim Scor 60
Compilator cpp Status done
Runda Arhiva educationala Marime 2.02 kb
#include <fstream>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;

#define NMax 1005
#define inf 2100000000

ifstream f("maxflow.in");
ofstream g("maxflow.out");

int n,m;
vector<int> v[NMax];
int C[NMax][NMax],F[NMax][NMax];
bool viz[NMax];
int ant[NMax];

int BFS()
{
    queue<int> cd;
    int i,s,semn,nod,nod2;
    int a=inf,b=inf,c;

    for(i=1;i<=n;i++) viz[i]=0;
    viz[1]=1;
    ant[1]=0;
    cd.push(1);
    while(!cd.empty())
    {
        s=cd.front(); cd.pop();

        for(i=0;i<(int)v[s].size();i++) if(!viz[v[s].at(i)])
        {
            semn=0;
            if(F[s][v[s].at(i)]<C[s][v[s].at(i)]) semn=1;
            if(!C[s][v[s].at(i)] && F[s][v[s].at(i)]) semn=-1;

            if(semn)
            {
                viz[v[s].at(i)]=1;
                ant[v[s].at(i)]=s*semn;

                if(v[s].at(i)==n)
                {
                    nod=n;
                    while(ant[nod])
                    {
                        nod2=abs(ant[nod]);

                        if(ant[nod]>0) a=min(a,C[nod2][nod]-F[nod2][nod]);
                        else b=min(b,F[nod][nod2]);

                        nod=nod2;
                    }

                    c=min(a,b);

                    nod=n;
                    while(ant[nod])
                    {
                        nod2=abs(ant[nod]);

                        if(ant[nod]>0) F[nod2][nod]+=c;
                        else F[nod][nod2]-=c;

                        nod=nod2;
                    }

                    return c;
                }

                cd.push(v[s].at(i));
            }
        }
    }

    return 0;
}

int main()
{
    int i;
    int a,b,c;
    int flow,fmin;

    f>>n>>m;
    for(i=1;i<=m;i++)
    {
        f>>a>>b>>c;
        C[a][b]=c;
        v[a].push_back(b);
        v[b].push_back(a);
    }

    for(flow=0;fmin=BFS();flow+=fmin);

    g<<flow<<"\n";

    f.close();
    g.close();
    return 0;
}