BZOJ 1797 最小割

struct node
{
    int u,v,cap,id,next;
};


node edges[N*50];
int head[N],e;


int pre[N],num[N],h[N],cur[N];
int s,t;


int Maxflow(int s,int t,int n)
{
    int i;
    for(i=0;i<n;i++) cur[i]=head[i];
    int u=s,Min,k,v,ans=0;
    while(h[u]<n)
    {
        if(u==t)
        {
            Min=INF;
            for(i=s;i!=t;i=edges[cur[i]].v)
            {
                k=cur[i];
                if(edges[k].cap<Min) Min=edges[k].cap,v=i;
            }
            ans+=Min; u=v;
            for(i=s;i!=t;i=edges[cur[i]].v)
            {
                k=cur[i];
                edges[k].cap-=Min;
                edges[k^1].cap+=Min;
            }
        }
        for(i=cur[u];i!=-1;i=edges[i].next)
        {
            if(edges[i].cap>0&&h[u]==h[edges[i].v]+1) break;
        }
        if(i!=-1)
        {
            cur[u]=i;
            pre[edges[i].v]=u;
            u=edges[i].v;
        }
        else
        {
            if(--num[h[u]]==0) break;
            cur[u]=head[u];
            Min=n;
            for(i=head[u];i!=-1;i=edges[i].next)
            {
                if(edges[i].cap>0&&h[edges[i].v]<Min) Min=h[edges[i].v];
            }
            h[u]=Min+1;
            num[Min+1]++;
            if(u!=s) u=pre[u];
        }
    }
    return ans;
}


int n,m;


void add(int u,int v,int w,int id)
{
    edges[e].u=u;
    edges[e].v=v;
    edges[e].cap=w;
    edges[e].id=id;
    edges[e].next=head[u];
    head[u]=e++;
}




int dfn[N],low[N],id,Num,color[N],visit[N];
stack<int> S;


void DFS(int u)
{
    low[u]=dfn[u]=++id;
    S.push(u);
    
    int i,v;
    for(i=head[u];i!=-1;i=edges[i].next) 
    {
        v=edges[i].v;
        if(edges[i].cap<=0) continue;
        if(!dfn[v])
        {
            DFS(v);
            low[u]=min(low[u],low[v]);
        }
        else if(!visit[v])
        {
            low[u]=min(low[u],dfn[v]);
        }
    }
    if(low[u]==dfn[u])
    {
        Num++;
        do
        {
            v=S.top();
            S.pop();
            visit[v]=1;
            color[v]=Num;
        }while(v!=u);
    }
}


int ans[N*30][2];


int main()
{
    clr(head,-1);
    RD(n,m); RD(s,t);
    int u,v,w,i;
    FOR1(i,m) 
    {
        RD(u,v,w);
        add(u,v,w,i);
        add(v,u,0,0);
    }
    Maxflow(s,t,n+1);
    FOR1(i,n) if(!visit[i]) DFS(i);
    FOR0(i,e)
    {
        u=edges[i].u;
        v=edges[i].v;
        w=edges[i].id;
        if(color[u]==color[v]) continue;
        if(edges[i].cap>0) continue;
        ans[w][0]=1;
        if(color[u]==color[s]&&color[v]==color[t]) 
        {
            ans[w][1]=1;
        }
    }
    FOR1(i,m) PR(ans[i][0],ans[i][1]);
}