【CF891C】Envy

题面

https://www.luogu.org/problem/CF891C

题解

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#define ri register int
#define N 500050
using namespace std;
struct edge {
  int u,v;int l;
} e[N];
int ide[N];
bool cmpide(int x,int y) {return e[x].l<e[y].l;}

struct cut {
  int id,q;
  bool operator < (const cut &rhs) const {
    if (e[id].l==e[rhs.id].l) return q<rhs.q; else return e[id].l<e[rhs.id].l;
  }
} tr[N<<2];

int n,m,top;
bool ans[N];

struct ss {
  int a,b,c,d;
};

struct binchaji {
  int f[N];int cen[N]; ss stk[N];
  void push(int x,int y) {
    stk[++top]=(ss){x,f[x],y,cen[y]};
    f[x]=y;
  }
  void clear() {
    for (ri i=1;i<=n;i++) f[i]=i,cen[i]=1;
  }
  int findroot(int x){
    if (f[x]==x) return x;
    return findroot(f[x]);
  }
  bool insert(int x) {
    int r1=findroot(e[x].u),r2=findroot(e[x].v);
    if (r1==r2) return 0;
    if (cen[r1]>cen[r2]) {
      push(r2,r1);
      cen[r1]=max(cen[r1],cen[r2]+1);
    }
    else {
      push(r1,r2);
      cen[r2]=max(cen[r2],cen[r1]+1);
    }
    return 1;
  }
  void back() {
    f[stk[top].a]=stk[top].b;
    cen[stk[top].c]=stk[top].d;
    top--;
  }
} bcj;

int main(){
  scanf("%d %d",&n,&m);
  for (ri i=1;i<=m;i++) scanf("%d %d %d",&e[i].u,&e[i].v,&e[i].l);
  for (ri i=1;i<=m;i++) ide[i]=i;
  sort(ide+1,ide+m+1,cmpide);
  int q;
  int cc=0;
  int k,x;
  scanf("%d",&q);
  for (ri i=1;i<=q;i++) {
    scanf("%d",&k);
    for (ri j=1;j<=k;j++) scanf("%d",&x),tr[++cc]=(cut){x,i};
  }
  sort(tr+1,tr+cc+1);
  memset(ans,1,sizeof(ans));
  int p=1; top=0;
  bcj.clear();
  for (ri i=1;i<=cc;i++) {
    if (e[tr[i].id].l!=e[tr[i-1].id].l) while (e[ide[p]].l<e[tr[i].id].l && p<=m) bcj.insert(ide[p]),p++;
    int ep,tot=0;
    for (ri j=i;tr[j].q==tr[i].q && e[tr[j].id].l==e[tr[i].id].l;j++) {
      if (!bcj.insert(tr[j].id)) ans[tr[i].q]=0; else tot++;
      ep=j;
    }
    while (tot) bcj.back(),tot--;
    i=ep;
  }
  for (ri i=1;i<=q;i++) if (ans[i]) puts("YES"); else puts("NO");
  return 0;
}