ISAP算法

struct EDGE{    int v,next,c,f;}E[maxn<<1];int head[maxn],tol;int gap[maxn],dep[maxn],pre[maxn],cur[maxn];void Init(){    memset(head,-1,sizeof head);    tol=0;}void add_edge(int u,int v,int f,int rf=0){    E[tol].v=v;    E[tol].c=f;    E[tol].f=0;    E[tol].next=head[u];    head[u]=tol++;    E[tol].v=u;    E[tol].c=rf;    E[tol].f=0;    E[tol].next=head[v];    head[v]=tol++;}int isap(int start,int end,int N){    memset(gap,0,sizeof gap);    memset(dep,0,sizeof dep);    memcpy(cur,head,sizeof head);    int u=start;    pre[u]=-1;    gap[0]=N;    int ans=0;    while(dep[start]<N){        if(u==end){            int Min=oo;            for(int i=pre[u];i!=-1;i=pre[E[i^1].v])                if(Min>E[i].c-E[i].f)                    Min=E[i].c-E[i].f;            for(int i=pre[u];i!=-1;i=pre[E[i^1].v]){                E[i].f+=Min;                E[i^1].f-=Min;            }            u=start;            ans+=Min;            continue;        }        bool flag=false;        int v;        for(int i=cur[u];i!=-1;i=E[i].next){            v=E[i].v;            if(E[i].c-E[i].f&&dep[v]+1==dep[u]){                flag=true;                cur[u]=pre[v]=i;                break;            }        }        if(flag){            u=v;            continue;        }        int Min=N;        for(int i=head[u];i!=-1;i=E[i].next)            if(E[i].c-E[i].f&&dep[E[i].v]<Min){                Min=dep[E[i].v];                cur[u]=i;