Luogu4897 【模板】最小割树

#include<iostream> 
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<map>
using namespace std;
int read()
{
    int x=0,f=1;char c=getchar();
    while (c<‘0‘||c>‘9‘) {if (c==‘-‘) f=-1;c=getchar();}
    while (c>=‘0‘&&c<=‘9‘) x=(x<<1)+(x<<3)+(c^48),c=getchar();
    return x*f;
}
#define N 510
#define M 1600
#define inf 1000000000
int n,m,p[N],v[N],u[N],tot=0,t=-1;
bool flag[N];
int d[N],cur[N],q[N];
struct data{int to,nxt,cap,flow;
}edge[M<<1];
map<int,bool> f;
namespace tree
{
    int p[N],fa[N],deep[N],len[N],t=0;
    struct data{int to,nxt,len;}edge[M<<1];
    void addedge(int x,int y,int z){t++;edge[t].to=y,edge[t].nxt=p[x],edge[t].len=z,p[x]=t;}
    void dfs(int k)
    {
        for (int i=p[k];i;i=edge[i].nxt)
        if (edge[i].to!=fa[k])
        {
            deep[edge[i].to]=deep[k]+1;
            fa[edge[i].to]=k;
            len[edge[i].to]=edge[i].len;
            dfs(edge[i].to);
        }
    }
    void solve(int q)
    {    
        while (q--)
        {
            int x=read(),y=read(),ans=100000000;
            if (deep[x]<deep[y]) swap(x,y);
            while (deep[x]>deep[y]) ans=min(ans,len[x]),x=fa[x];
            while (x!=y) ans=min(ans,len[x]),ans=min(ans,len[y]),x=fa[x],y=fa[y];
            printf("%d\n",ans);
        }
    }
}
void addedge(int x,int y,int z)
{
    t++;edge[t].to=y,edge[t].nxt=p[x],edge[t].cap=z,edge[t].flow=0,p[x]=t;
}
bool bfs(int S,int T)
{
    memset(d,255,sizeof(d));d[S]=0;
    int head=0,tail=1;q[1]=S;
    do
    {
        int x=q[++head];
        for (int i=p[x];~i;i=edge[i].nxt)
        if (d[edge[i].to]==-1&&edge[i].flow<edge[i].cap)
        {
            d[edge[i].to]=d[x]+1;
            q[++tail]=edge[i].to;
        }
    }while (head<tail);
    return ~d[T];
}
int work(int k,int T,int f)
{
    if (k==T) return f;
    int used=0;
    for (int i=cur[k];~i;i=edge[i].nxt)
    if (d[k]+1==d[edge[i].to])
    {
        int w=work(edge[i].to,T,min(f-used,edge[i].cap-edge[i].flow));
        edge[i].flow+=w,edge[i^1].flow-=w;
        if (edge[i].flow<edge[i].cap) cur[k]=i;
        used+=w;if (used==f) return f;
    }
    if (used==0) d[k]=-1;
    return used;
}
void dinic(int S,int T)
{
    for (int i=0;i<=t;i++) edge[i].flow=0;
    int ans=0;
    while (bfs(S,T))
    {
        memcpy(cur,p,sizeof(p));
        ans+=work(S,T,inf);
    }
    tree::addedge(S,T,ans);
}
void dfs(int k)
{
    flag[k]=1;
    for (int i=p[k];~i;i=edge[i].nxt)
    if (!flag[edge[i].to]&&edge[i].flow<edge[i].cap)
    dfs(edge[i].to);
}
void solve(int l,int r)
{
    if (l>=r) return;
    dinic(v[l],v[r]);
    memset(flag,0,sizeof(flag));
    dfs(v[l]);
    int cnt=l-1;
    for (int i=l;i<=r;i++)
    if (flag[v[i]]) u[++cnt]=v[i];
    cnt=r+1;
    for (int i=l;i<=r;i++)
    if (!flag[v[i]]) u[--cnt]=v[i];
    for (int i=l;i<=r;i++) v[i]=u[i];
    solve(l,cnt-1);
    solve(cnt,r);
}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("mincuttree.in","r",stdin);
    freopen("mincuttree.out","w",stdout);
    const char LL[]="%I64d\n";
#else
    const char LL[]="%lld\n";
#endif
    n=read(),m=read();
    memset(p,255,sizeof(p));
    for (int i=1;i<=m;i++)
    {
        int x=read(),y=read(),z=read();
        addedge(x,y,z),addedge(y,x,z);
    }
    for (int i=1;i<=n;i++) v[i]=i;
    solve(1,n);
    tree::dfs(1);
    int q=read();
    tree::solve(q);
    return 0;
}