网络流模板

namespace NetFlow
{
const int MAXN=100000,MAXM=100000,inf=1e9;
struct Edge
{
int v,c,f,nx;
Edge() {}
Edge(int v,int c,int f,int nx):v(v),c(c),f(f),nx(nx) {}
} E[MAXM];
int G[MAXN],cur[MAXN],pre[MAXN],dis[MAXN],gap[MAXN],N,sz;
void init(int _n)
{
N=_n,sz=0; memset(G,-1,sizeof(G[0])*N);
}
void link(int u,int v,int c)
{
E[sz]=Edge(v,c,0,G[u]); G[u]=sz++;
E[sz]=Edge(u,0,0,G[v]); G[v]=sz++;
}
int ISAP(int S,int T)
{//S -> T
int maxflow=0,aug=inf,flag=false,u,v;
for (int i=0;i<N;++i)cur[i]=G[i],gap[i]=dis[i]=0;
for (gap[S]=N,u=pre[S]=S;dis[S]<N;flag=false)
{
for (int &it=cur[u];~it;it=E[it].nx)
{
if (E[it].c>E[it].f&&dis[u]==dis[v=E[it].v]+1)
{
if (aug>E[it].c-E[it].f) aug=E[it].c-E[it].f;
pre[v]=u,u=v; flag=true;
if (u==T)
{
for (maxflow+=aug;u!=S;)
{
E[cur[u=pre[u]]].f+=aug;
E[cur[u]^1].f-=aug;
}
aug=inf;
}
break;
}
}
if (flag) continue;
int mx=N;
for (int it=G[u];~it;it=E[it].nx)
{
if (E[it].c>E[it].f&&dis[E[it].v]<mx)
{
mx=dis[E[it].v]; cur[u]=it;
}
}
if ((--gap[dis[u]])==0) break;
++gap[dis[u]=mx+1]; u=pre[u];
}
return maxflow;
}
bool bfs(int S,int T)
{
static int Q[MAXN]; memset(dis,-1,sizeof(dis[0])*N);
dis[S]=0; Q[0]=S;
for (int h=0,t=1,u,v,it;h<t;++h)
{
for (u=Q[h],it=G[u];~it;it=E[it].nx)
{
if (dis[v=E[it].v]==-1&&E[it].c>E[it].f)
{
dis[v]=dis[u]+1; Q[t++]=v;
}
}
}
return dis[T]!=-1;
}
int dfs(int u,int T,int low)
{
if (u==T) return low;
int ret=0,tmp,v;
for (int &it=cur[u];~it&&ret<low;it=E[it].nx)
{
if (dis[v=E[it].v]==dis[u]+1&&E[it].c>E[it].f)
{
if (tmp=dfs(v,T,min(low-ret,E[it].c-E[it].f)))
{
ret+=tmp; E[it].f+=tmp; E[it^1].f-=tmp;
}
}
}
if (!ret) dis[u]=-1; return ret;
}
int dinic(int S,int T)
{
int maxflow=0,tmp;
while (bfs(S,T))
{
memcpy(cur,G,sizeof(G[0])*N);
while (tmp=dfs(S,T,inf)) maxflow+=tmp;
}
return maxflow;
}
}