ISAP模板

int head[N],cur[N],pre[N],d[N],gap[N];
int n,m,hcnt,S,T;
struct Node{
    int to,nxt,v;
    Node(){}
    Node(int a,int b,int c):to(a),nxt(b),v(c){}
}node[maxn];
inline void add(int x,int y,int v){
    node[hcnt]=Node(y,head[x],v);head[x]=hcnt++;
    node[hcnt]=Node(x,head[y],0);head[y]=hcnt++;
}
bool ISAP(int S,int T,int n){ ///起点,终点,总共点数(加上源汇点)
    int ans=0,aug=inf,i,flag; ///最大流,可增广流量,.,标记
    int u,e,dis;              ///当前点,当前可达点
    mst(gap,0);mst(d,0);
    for(i=0;i<=n;++i) cur[i]=head[i];
    u=pre[S]=S;
    while(d[S]<n){
        flag=0;
        for(i=cur[u];~i;i=node[i].nxt){
            e=node[i].to;
            if(node[i].v>0&&d[u]==d[e]+1){
                flag=1;
                break;
            }
        }
        if(flag){
            pre[e]=u;
            cur[u]=i;
            aug=min(aug,node[i].v);
            u=e;
            if(u==T){
                while(u!=S){
                    u=pre[u];
                    node[cur[u]].v-=aug;
                    node[cur[u]^1].v+=aug;
                }
                u=S;
                ans+=aug;
                aug=inf;
            }
        }
        else{
            if(--gap[d[u]]==0)break;
            dis=n;
            cur[u]=head[u];
            for(int i=head[u];~i;i=node[i].nxt){
                e=node[i].to;
                if(node[i].v>0&&d[e]+1<dis){
                    dis=d[e]+1;
                    cur[u]=i;
                }
            }
            d[u]=dis;
            ++gap[dis];
            if(u!=S)
                u=pre[u];
        }
    }
    return ans;
}