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：

  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstring>
  4 #include<algorithm>
  5 #include<queue>
  6 using namespace std;
  7 #define MAXN 44444
  8 #define MAXM 999999
  9 #define inf 1<<30
 10 
 11 struct Edge {
 12     int v,cap,next;
 13 } edge[MAXM];
 14 
 15 int n,m,vs,vt,NE,NV;
 16 int head[MAXN];
 17 
 18 void Insert(int u,int v,int cap)
 19 {
 20     edge[NE].v=v;
 21     edge[NE].cap=cap;
 22     edge[NE].next=head[u];
 23     head[u]=NE++;
 24 
 25     edge[NE].v=u;
 26     edge[NE].cap=0;
 27     edge[NE].next=head[v];
 28     head[v]=NE++;
 29 }
 30 
 31 int level[MAXN];
 32 int gap[MAXN];
 33 
 34 void bfs(int vt)
 35 {
 36     memset(level,-1,sizeof(level));
 37     memset(gap,0,sizeof(gap));
 38     level[vt]=0;
 39     gap[level[vt]]++;
 40     queue<int>que;
 41     que.push(vt);
 42     while(!que.empty()) {
 43         int u=que.front();
 44         que.pop();
 45         for(int i=head[u]; i!=-1; i=edge[i].next) {
 46             int v=edge[i].v;
 47             if(level[v]!=-1)continue;
 48             level[v]=level[u]+1;
 49             gap[level[v]]++;
 50             que.push(v);
 51 
 52         }
 53     }
 54 }
 55 
 56 
 57 int pre[MAXN];
 58 int cur[MAXN];
 59 
 60 int SAP(int vs,int vt)
 61 {
 62     bfs(vt);
 63     memset(pre,-1,sizeof(pre));
 64     memcpy(cur,head,sizeof(head));
 65     int u=pre[vs]=vs,flow=0,aug=inf;
 66     gap[0]=NV;
 67     while(level[vs]<NV) {
 68         bool flag=false;
 69         for(int &i=cur[u]; i!=-1; i=edge[i].next) {
 70             int v=edge[i].v;
 71             if(edge[i].cap&&level[u]==level[v]+1) {
 72                 flag=true;
 73                 pre[v]=u;
 74                 u=v;
 75                 //  aug=(aug==-1?edge[i].cap:min(aug,edge[i].cap));
 76                 aug=min(aug,edge[i].cap);
 77                 if(v==vt) {
 78                     flow+=aug;
 79                     for(u=pre[v]; v!=vs; v=u,u=pre[u]) {
 80                         edge[cur[u]].cap-=aug;
 81                         edge[cur[u]^1].cap+=aug;
 82                     }
 83                     //     aug=-1;
 84                     aug=inf;
 85                 }
 86                 break;
 87             }
 88         }
 89         if(flag)continue;
 90         int minlevel=NV;
 91         for(int i=head[u]; i!=-1; i=edge[i].next) {
 92             int v=edge[i].v;
 93             if(edge[i].cap&&level[v]<minlevel) {
 94                 minlevel=level[v];
 95                 cur[u]=i;
 96             }
 97         }
 98         if(--gap[level[u]]==0)break;
 99         level[u]=minlevel+1;
100         gap[level[u]]++;
101         u=pre[u];
102     }
103     return flow;
104 }
105 
106 
107 int main()
108 {
109     int u,v,w,w1,w2;
110     scanf("%d%d",&n,&m);
111     vs=0;
112     vt=n+1;
113     NV=n+2;
114     NE=0;
115     memset(head,-1,sizeof(head));
116     for(int i=1; i<=n; i++) {
117         scanf("%d%d",&w1,&w2);
118         Insert(vs,i,w1);
119         Insert(i,vt,w2);
120     }
121     for(int i=1; i<=m; i++) {
122         scanf("%d%d%d",&u,&v,&w);
123         Insert(u,v,w);
124         Insert(v,u,w);
125     }
126     printf("%d\n",SAP(vs,vt));
127     return 0;
128 }