zkw費用流
阿新 • • 發佈:2019-01-29
inline bool SPFA()
{
memset(dis,0x3f,sizeof(dis));
dis[T]=0;q.push(T);
while(!q.empty())
{
int tmp=q.front();q.pop();
b[tmp]=0;
for(int i=head[tmp];i;i=a[i].nxt)
if(dis[a[i].to]>dis[tmp]+a[i^1].cost&&a[i^1].remain)
{
dis[a[i].to ]=dis[tmp]+a[i^1].cost;
if(!b[a[i].to]) b[a[i].to]=1,q.push(a[i].to);
}
}
return dis[S]<INF;
}
int dfs(int now,int limit,int cost)
{
vis[now]=1;
if(now==T||!limit) return ans2+=limit*cost,limit;
int flow=0,f;
for(int i=head[now];i;i=a[i].nxt)
if(dis[now ]-a[i].cost==dis[a[i].to]&&a[i].remain&&!vis[a[i].to]&&(f=dfs(a[i].to,min(limit,a[i].remain),cost+a[i].cost)))
{
limit-=f,flow+=f,a[i].remain-=f,a[i^1].remain+=f;
if(!limit) return flow;
}
dis[now]=-1;return flow;
}
inline void zkw()
{
while (SPFA())
do
{
memset(vis,0,sizeof(vis));
ans1+=dfs(S,INF,0);
}
while(vis[T]);
}