SAP模板

#include<iostream>#include<cstring>#include<cstdio>using namespace std;const int MAXN=20010;//点数的最大值const int MAXM=880010;//边数的最大值const int INF=0x7fffffff;struct Node{    int from,to,next;    int cap;}edge[MAXM];int tol;int head[MAXN];int dep[MAXN];int gap[MAXN];//gap[x]=y :说明残留网络中dep[i]==x的个数为yint n;//n是总的点的个数，包括源点和汇点void init(){    tol=0;    memset(head,-1,sizeof(head));}void addedge(int u,int v,int w){    edge[tol].from=u;    edge[tol].to=v;    edge[tol].cap=w;    edge[tol].next=head[u];    head[u]=tol++;    edge[tol].from=v;    edge[tol].to=u;    edge[tol].cap=0;    edge[tol].next=head[v];    head[v]=tol++;}void BFS(int start,int end){    memset(dep,-1,sizeof(dep));    memset(gap,0,sizeof(gap));    gap[0]=1;    int que[MAXN];    int front,rear;    front=rear=0;    dep[end]=0;    que[rear++]=end;    while(front!=rear)    {        int u=que[front++];        if(front==MAXN)front=0;        for(int i=head[u];i!=-1;i=edge[i].next)        {            int v=edge[i].to;            if(dep[v]!=-1)continue;            que[rear++]=v;            if(rear==MAXN)rear=0;            dep[v]=dep[u]+1;            ++gap[dep[v]];        }    }}int SAP(int start,int end){    int res=0;    BFS(start,end);    int cur[MAXN];    int S[MAXN];    int top=0;    memcpy(cur,head,sizeof(head));    int u=start;    int i;    while(dep[start]<n)    {        if(u==end)        {            int temp=INF;            int inser;            for(i=0;i<top;i++)               if(temp>edge[S[i]].cap)               {                   temp=edge[S[i]].cap;                   inser=i;               }            for(i=0;i<top;i++)            {                edge[S[i]].cap-=temp;                edge[S[i]^1].cap+=temp;            }            res+=temp;            top=inser;            u=edge[S[top]].from;        }        if(u!=end&&gap[dep[u]-1]==0)//出现断层，无增广路          break;        for(i=cur[u];i!=-1;i=edge[i].next)           if(edge[i].cap!=0&&dep[u]==dep[edge[i].to]+1)             break;        if(i!=-1)        {            cur[u]=i;            S[top++]=i;            u=edge[i].to;        }        else        {            int min=n;            for(i=head[u];i!=-1;i=edge[i].next)            {                if(edge[i].cap==0)continue;                if(min>dep[edge[i].to])                {                    min=dep[edge[i].to];                    cur[u]=i;                }            }            --gap[dep[u]];            dep[u]=min+1;            ++gap[dep[u]];            if(u!=start)u=edge[S[--top]].from;        }    }    return res;}