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 }

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