POJ 1273 Drainage Ditches | 最大流模板

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<queue>
#define N 250
#define M 250
#define INF 100000000
using namespace std;
int head[N],cur[N],lev[N],ecnt=1,S,T,n,m;
queue <int> q;
struct adj
{
    int nxt,v,w;
}e[2*M];
void add(int u,int v,int w)
{
    e[++ecnt].v=v,e[ecnt].w=w,e[ecnt].nxt=head[u],head[u]=ecnt;
    e[++ecnt].v=u,e[ecnt].w=0,e[ecnt].nxt=head[v],head[v]=ecnt;
}
inline int bfs()
{
    int u,v;
    for (int i=S;i<=T;i++)
	lev[i]=-1,cur[i]=head[i];
    q.push(S),lev[S]=0;
    while (!q.empty())
    {
	u=q.front();
	for (int i=head[u];i;i=e[i].nxt)
	{
	    if (e[i].w>0 && lev[v=e[i].v]==-1)
		lev[v]=lev[u]+1,q.push(v);
	}
	q.pop();
    }
    return lev[T]!=-1;
}
inline int Dinic(const int &u,const int &flow)
{
    if (u==T) return flow;
    int res=0,v,delta;
    for (int &i=cur[u];i;i=e[i].nxt)
    {
	if (e[i].w>0 && lev[u]<lev[v=e[i].v])
	{
	    delta=Dinic(v,min(e[i].w,flow-res));
	    if (delta)
	    {
		e[i].w-=delta;e[i^1].w+=delta;
		res+=delta;if (res==flow) break;
	    }
	}
    }
    if (res!=flow) lev[u]=-1;
    return res;
}
inline int Maxflow()
{
    int ans=0;
    while (bfs()) ans+=Dinic(S,INF);
    return ans;
}
inline void init()
{
    memset(head,0,sizeof(head));
    ecnt=1;
}
int main()
{
    while (scanf("%d%d",&n,&m)!=EOF)
    {
	init();
	for (int i=1,x,y,z;i<=n;i++)
	{
	    scanf("%d%d%d",&x,&y,&z);
	    add(x,y,z);
	}
	S=1,T=m;
	printf("%d
",Maxflow());
    }
    return 0;
}