> 建图的时候已经把输入 和输出边的点分开了 就是不知道怎么继续了！！求教啊！
> #include <iostream>
> using namespace std;
> const int maxn=60500;
> const int inf=1<<30;
> struct edge
> {
> 	int from,to,val,next;
> }map[maxn];
> int vis[500],que[500],dist[500],len;
> int wIn[500],wOut[500];
> int mark[500];
> int S,T;
> int M,N;
> int edg[5001][2];
> void init()
> {
> 	len=0;
> 	memset(vis,-1,sizeof(vis));
> }
> void insert (int from,int to,int val)    //从from 到  to
> {
> 	map[len].from=from;
> 	map[len].to=to;
> 	map[len].val=val;
> 	map[len].next=vis[from];
> 	vis[from]=len++;
> 	map[len].from=to;
> 	map[len].to=from;
> 	map[len].val=0;
> 	map[len].next=vis[to];
> 	vis[to]=len++;
> }
> int Dinic(int n,int s,int t)
> {
> 	int ans=0;
> 	while(true)
> 	{
> 		int head,tail,id,i;
> 		head=tail=0;
> 		que[tail++]=s;
> 		memset(dist,-1,sizeof(dist));
> 		dist[s]=0;
> 		while(head<tail)
> 		{
> 			id=vis[que[head++]];
> 			while(id!=-1)
> 			{
> 				if(map[id].val>0&&dist[map[id].to]==-1)
> 				{
> 					dist[map[id].to]=dist[map[id].from]+1;
> 					que[tail++]=map[id].to;
> 					if(map[id].to==t)
> 					{
> 						head=tail;
> 						break;
> 					}
> 				}
> 				id=map[id].next;
> 			}
> 		}
> 		if(dist[t]==-1)
> 			break;
> 		id=s,tail=0;
> 		while(true)
> 		{
> 			if(id==t)       //找到一条增广路
> 			{
> 				int flow=inf,fir;
> 				for(i=0;i<tail;i++)
> 					if(map[que[i]].val<flow)
> 					{
> 						fir=i;
> 						flow=map[que[i]].val;
> 					}
> 					for(i=0;i<tail;i++)
> 						map[que[i]].val-=flow,map[que[i]^1].val+=flow;
> 					ans+=flow;
> 					tail=fir;
> 					id=map[que[fir]].from;
> 			}
> 			id=vis[id];
> 			while(id!=-1)
> 			{
> 				if(map[id].val>0&&dist[map[id].from]+1==dist[map[id].to])
> 					break;
> 				id=map[id].next;
> 			}
> 			if(id!=-1)
> 			{
> 				que[tail++]=id;
> 				id=map[id].to;
> 			}
> 			else
> 			{
> 				if(tail==0)
> 					break;
> 				dist[map[que[tail-1]].to]=-1;
> 				id=map[que[--tail]].from;
> 			}
> 		}
> 	}
> 	return ans;
> }
> void CreatGraph()
> {// 建图
> 	int i, ii;
> 	S = 0;
> 	T = 2 * N + 1;
> 	len = 0;
> 	for (i = 1; i <= N; i++)
> 	{
> 		ii = i + N;
> 		insert(S, ii, wOut[i]);
> 		insert(i, T, wIn[i]);
> 	}
> 	for (i = 1; i <= M; i++)
> 	{
> 		ii = edg[i][0] + N;
> 		insert(ii, edg[i][1], 0xffffff);
> 	}
> }
> int main()
> {
> 	init();
> 	int i, num;
>     int cnt[500];
> 	scanf("%d%d", &N, &M);
> 	for (i = 1; i <= N; i++)
> 		scanf("%d", &wIn[i]);
>     for (i = 1; i <= N; i++)
> 		scanf("%d", &wOut[i]);
>     for (i = 1; i <= M; i++)
>         scanf("%d%d", &edg[i][0], &edg[i][1]);
> 	CreatGraph();	
> 	int ans=Dinic(T,S,T);
> 	cout<<ans<<endl;
> 	return 0;
> }
dfs（）找割点