1 const int MAXN=20010;//點數的最大值
  2 const int MAXM=880010;//邊數的最大值
  3 const int INF=0x3f3f3f3f;
  4 
  5 struct Node
  6 {
  7     int from,to,next;
  8     int cap;
  9 }edge[MAXM];
 10 int tol;
 11 int head[MAXN];
 12 int dep[MAXN];
 13 int gap[MAXN];//gap[x]=y :說明殘留網絡中dep[i]==x的個數為y
 14 
 15 int n;//n是總的點的個數，包括源點和匯點
 16 
 17 void init()
 18 {
 19     tol=0;
 20     memset(head,-1,sizeof(head));
 21 }
 22 
 23 void addedge(int u,int v,int w)
 24 {
 25     edge[tol].from=u;
 26     edge[tol].to=v;
 27     edge[tol].cap=w;
 28     edge[tol].next=head[u];
 29     head[u]=tol++;
 30     edge[tol].from=v;
 31     edge[tol].to=u;
 32     edge[tol].cap=0;
 33     edge[tol].next=head[v];
 34     head[v]=tol++;
 35 }
 36 void BFS(int start,int end)
 37 {
 38     memset(dep,-1,sizeof(dep));
 39     memset(gap,0,sizeof(gap));
 40     gap[0]=1;
 41     int que[MAXN];
 42     int front,rear;
 43     front=rear=0;
 44     dep[end]=0;
 45     que[rear++]=end;
 46     while(front!=rear)
 47     {
 48         int u=que[front++];
 49         if(front==MAXN)front=0;
 50         for(int i=head[u];i!=-1;i=edge[i].next)
 51         {
 52             int v=edge[i].to;
 53             if(dep[v]!=-1)continue;
 54             que[rear++]=v;
 55             if(rear==MAXN)rear=0;
 56             dep[v]=dep[u]+1;
 57             ++gap[dep[v]];
 58         }
 59     }
 60 }
 61 int SAP(int start,int end)
 62 {
 63     int res=0;
 64     BFS(start,end);
 65     int cur[MAXN];
 66     int S[MAXN];
 67     int top=0;
 68     memcpy(cur,head,sizeof(head));
 69     int u=start;
 70     int i;
 71     while(dep[start]<n)
 72     {
 73         if(u==end)
 74         {
 75             int temp=INF;
 76             int inser;
 77             for(i=0;i<top;i++)
 78                if(temp>edge[S[i]].cap)
 79                {
 80                    temp=edge[S[i]].cap;
 81                    inser=i;
 82                }
 83             for(i=0;i<top;i++)
 84             {
 85                 edge[S[i]].cap-=temp;
 86                 edge[S[i]^1].cap+=temp;
 87             }
 88             res+=temp;
 89             top=inser;
 90             u=edge[S[top]].from;
 91         }
 92         if(u!=end&&gap[dep[u]-1]==0)//出現斷層，無增廣路
 93           break;
 94         for(i=cur[u];i!=-1;i=edge[i].next)
 95            if(edge[i].cap!=0&&dep[u]==dep[edge[i].to]+1)
 96              break;
 97         if(i!=-1)
 98         {
 99             cur[u]=i;
100             S[top++]=i;
101             u=edge[i].to;
102         }
103         else
104         {
105             int min=n;
106             for(i=head[u];i!=-1;i=edge[i].next)
107             {
108                 if(edge[i].cap==0)continue;
109                 if(min>dep[edge[i].to])
110                 {
111                     min=dep[edge[i].to];
112                     cur[u]=i;
113                 }
114             }
115             --gap[dep[u]];
116             dep[u]=min+1;
117             ++gap[dep[u]];
118             if(u!=start)u=edge[S[--top]].from;
119         }
120     }
121     return res;
122 }