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Cod sursa(job #698056)
#include <fstream>
#include <vector>
#include <queue>
using namespace std;
const int N=65,inf=1<<30;
int drum[N][N],cap[N][N],flux[N][N],cost[N][N],grad[N],T[N],dist[N],n;
struct Muchie
{
int y,c;
};
vector<int> a[N];
vector<Muchie> b[N];
queue<int> Q;
ifstream in("traseu.in");
ofstream out("traseu.out");
inline int dif(int x,int y)
{
return cap[x][y]-flux[x][y];
}
inline int min(int a,int b)
{
return a<b ? a : b;
}
bool bf(int x,int D)
{
for (int i=1;i<=n+1;i++)
dist[i]=T[i]=inf;
while (!Q.empty())
Q.pop();
dist[x]=0;
Q.push(x);
while (!Q.empty())
{
x=Q.front();
Q.pop();
if (x==D)
return true;
for (vector<int>::iterator i=a[x].begin();i!=a[x].end();i++)
if (dif(x,*i)>0 && dist[x]+cost[x][*i]<dist[*i])
{
dist[*i]=dist[x]+cost[x][*i];
T[*i]=x;
Q.push(*i);
}
}
return false;
}
int flow(int S,int D)
{
int C=0,M;
while (bf(S,D))
{
M=inf;
for (int i=D;i!=S;i=T[i])
M=min(M,dif(T[i],i));
for (int i=D;i!=S;i=T[i])
{
flux[T[i]][i]+=M;
flux[i][T[i]]-=M;
C+=M*cost[T[i]][i];
}
}
return C;
}
inline int scor (int x,int y,int z)
{
return (x && y && (!z || x+y<z)) ? x+y : z;
}
void bellman_ford(int dist[],int x)
{
int y,c;
for (int i=1;i<=n;i++)
dist[i]=inf;
dist[x]=0;
Q.push(x);
while (!Q.empty())
{
x=Q.front();
Q.pop();
for (vector<Muchie>::iterator i=b[x].begin();i!=b[x].end();i++)
{
y=(*i).y;
c=(*i).c;
if (dist[x]+c<dist[y])
{
dist[y]=dist[x]+c;
Q.push(y);
}
}
}
}
int main()
{
int m,x,y,c,C=0;
in>>n>>m;
while (m--)
{
in>>x>>y>>c;
b[x].push_back((Muchie){y,c});
C+=c;
grad[x]++;
grad[y]--;
}
for (int i=1;i<=n;++i)
bellman_ford(drum[i],i);
for (int i=1;i<=n;i++)
if (grad[i]<0)
{
cap[0][i]=-grad[i];
a[0].push_back(i);
a[i].push_back(0);
for (int j=1;j<=n;j++)
if (grad[j]>0)
{
cap[i][j]=inf;
cost[i][j]=drum[i][j];
a[i].push_back(j);
a[j].push_back(i);
}
}
else
{
cap[i][n+1]=grad[i];
a[n+1].push_back(i);
a[i].push_back(n+1);
}
out<<C+flow(0,n+1)<<"\n";
return 0;
}