poj 3469(网络流模版)

题目链接：http://poj.org/problem?id=3469

思路：终于把网络流的模版测试好了，在Dinic和Sap之间还是选择了Sap,事实证明Sap确实比Dinic效率高，在此贴出自己的网络流模版：

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<queue>
 using namespace std;
 #define MAXN 44444
 #define MAXM 999999
 #define inf 1<<30

 struct Edge {
     int v,cap,next;
 } edge[MAXM];

 int n,m,vs,vt,NE,NV;
 int head[MAXN];

 void Insert(int u,int v,int cap)
 {
     edge[NE].v=v;
     edge[NE].cap=cap;
     edge[NE].next=head[u];
     head[u]=NE++;

     edge[NE].v=u;
     edge[NE].cap=;
     edge[NE].next=head[v];
     head[v]=NE++;
 }

 int level[MAXN];
 int gap[MAXN];

 void bfs(int vt)
 {
     memset(level,-,sizeof(level));
     memset(gap,,sizeof(gap));
     level[vt]=;
     gap[level[vt]]++;
     queue<int>que;
     que.push(vt);
     while(!que.empty()) {
         int u=que.front();
         que.pop();
         for(int i=head[u]; i!=-; i=edge[i].next) {
             int v=edge[i].v;
             if(level[v]!=-)continue;
             level[v]=level[u]+;
             gap[level[v]]++;
             que.push(v);

         }
     }
 }

 int pre[MAXN];
 int cur[MAXN];

 int SAP(int vs,int vt)
 {
     bfs(vt);
     memset(pre,-,sizeof(pre));
     memcpy(cur,head,sizeof(head));
     int u=pre[vs]=vs,flow=,aug=inf;
     gap[]=NV;
     while(level[vs]<NV) {
         bool flag=false;
         for(int &i=cur[u]; i!=-; i=edge[i].next) {
             int v=edge[i].v;
             if(edge[i].cap&&level[u]==level[v]+) {
                 flag=true;
                 pre[v]=u;
                 u=v;
                 //  aug=(aug==-1?edge[i].cap:min(aug,edge[i].cap));
                 aug=min(aug,edge[i].cap);
                 if(v==vt) {
                     flow+=aug;
                     for(u=pre[v]; v!=vs; v=u,u=pre[u]) {
                         edge[cur[u]].cap-=aug;
                         edge[cur[u]^].cap+=aug;
                     }
                     //     aug=-1;
                     aug=inf;
                 }
                 break;
             }
         }
         if(flag)continue;
         int minlevel=NV;
         for(int i=head[u]; i!=-; i=edge[i].next) {
             int v=edge[i].v;
             if(edge[i].cap&&level[v]<minlevel) {
                 minlevel=level[v];
                 cur[u]=i;
             }
         }
         if(--gap[level[u]]==)break;
         level[u]=minlevel+;
         gap[level[u]]++;
         u=pre[u];
     }
     return flow;
 }

 int main()
 {
     int u,v,w,w1,w2;
     scanf("%d%d",&n,&m);
     vs=;
     vt=n+;
     NV=n+;
     NE=;
     memset(head,-,sizeof(head));
     for(int i=; i<=n; i++) {
         scanf("%d%d",&w1,&w2);
         Insert(vs,i,w1);
         Insert(i,vt,w2);
     }
     for(int i=; i<=m; i++) {
         scanf("%d%d%d",&u,&v,&w);
         Insert(u,v,w);
         Insert(v,u,w);
     }
     printf("%d\n",SAP(vs,vt));
     return ;
 }