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dinic

//HDU 3549
int dis[N],vis[N],clock;
int st,ed;
queue<int> qq;
int bfs(){
    clock++;
    qq.push(st);vis[st]=clock;dis[st]=0;
    while(!qq.empty()){
        int u=qq.front();qq.pop();
        for(int i=head[u];i!=-1;i=e[i].next){
            int v=e[i].v;
            if(e[i].cap&&vis[v]!=clock){
                vis[v]=clock;
                dis[v]=dis[u]+1;
                qq.push(v);
            }
        }
    }
    return vis[ed]==clock;
}

int cur[N];
int dfs(int u,int pre){
    if(u==ed||pre==0)return pre;
    int flow=0;
    for(int &i=cur[u];i!=-1;i=e[i].next){
        int v=e[i].v;
        if(e[i].cap&&dis[v]==dis[u]+1){
            int f=dfs(v,min(pre,e[i].cap));
            e[i].cap-=f;
            e[i^1].cap+=f;
            pre-=f;
            flow+=f;
        }
        if(pre==0)break;
    }
    return flow;
}

int dinic(int n){
    int flow=0;
    clock=0;
    memset(vis,0,sizeof(vis));
    while(bfs()){
        for(int i=0;i<n;i++)cur[i]=head[i];
        flow+=dfs(st,INF);
    }
    return flow;
}

ispa

//HDU 3549
int cur[N],gap[N],dis[N],pre[N];

int isap(int st,int ed,int n){

    int flow=0;
    for(int i=0; i<n; i++){
        dis[i]=gap[i]=0;
        cur[i]=head[i];
    }
    int u=pre[st]=st;
    int aug=INF;
    gap[0]=n;
    while(dis[st]<n){
loop:
        for(int &i=cur[u]; i!=-1; i=e[i].next){
            int v=e[i].v;
            if(e[i].cap>0 && dis[u]==dis[v]+1){
                aug=min(aug,e[i].cap);
                pre[v]=u;
                u=v;
                if(v==ed){
                    flow+=aug;
                    for(u=pre[u]; v!=st; v=u,u=pre[u]){
                        e[cur[u]].cap-=aug;
                        e[cur[u]^1].cap+=aug;
                    }
                    aug=INF;
                }
                goto loop;
            }
        }
        int mm=n-1;
        for(int i=head[u]; i!=-1; i=e[i].next){
            int v=e[i].v;
            if(e[i].cap>0 && mm>dis[v]){
                cur[u]=i;
                mm=dis[v];
            }
        }
        if(--gap[dis[u]]==0) break;
        gap[dis[u]=mm+1]++;
        u=pre[u];
    }
    return flow;
}