CF375D Tree and Queries

Posted 2022-03-23 mle-world

树上莫队板子题，求个\(dfn\)求个\(low\)就行了。

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<algorithm>
#include<queue>
#include<set>
#include<map>
#include<iostream>
using namespace std;
#define re register
#define ll long long
inline int gi()
    int f=1,sum=0;char ch=getchar();
    while(ch>'9' || ch<'0')if(ch=='-')f=-1;ch=getchar();
    while(ch>='0' && ch<='9')sum=(sum<<3)+(sum<<1)+ch-'0';ch=getchar();
    return f*sum;

const int N=100010;
int front[N],cnt,bl[N],n,m,c[N],ans[N];
struct nodeint to,nxt;e[N<<1];
void Add(int u,int v)e[++cnt]=(node)v,front[u];front[u]=cnt;
struct point
    int dfn,low,c;
    bool operator<(const point &b)constreturn dfn<b.dfn;
a[N];
struct ques
    int l,r,k,id;
    bool operator<(const ques &b)constreturn bl[l]==bl[b.l]?r<b.r:l<b.l;
q[N];
int Time;
void dfs(int u,int ff)
    a[u].dfn=++Time;a[u].c=c[u];
    for(int i=front[u];i;i=e[i].nxt)
        int v=e[i].to;if(v==ff)continue;
        dfs(v,u);
    
    a[u].low=Time;

int B,sum[N],tot[N];
void Add(int x)sum[++tot[x]]++;
void Del(int x)sum[tot[x]--]--;
int main()
    n=gi();m=gi();B=sqrt(n);for(int i=1;i<=n;i++)c[i]=gi();
    for(int i=1;i<=n;i++)bl[i]=(i-1)/B+1;
    for(int i=1;i<n;i++)int u=gi(),v=gi();Add(u,v);Add(v,u);
    dfs(1,1);
    for(int i=1;i<=m;i++)int u=gi(),k=gi();q[i].l=a[u].dfn;q[i].r=a[u].low;q[i].k=k;q[i].id=i;
    sort(q+1,q+m+1);sort(a+1,a+n+1);
    for(int i=1,l=1,r=0;i<=m;i++)
        while(l<q[i].l)Del(a[l++].c);
        while(l>q[i].l)Add(a[--l].c);
        while(r<q[i].r)Add(a[++r].c);
        while(r>q[i].r)Del(a[r--].c);
        ans[q[i].id]=sum[q[i].k];
    
    for(int i=1;i<=m;i++)printf("%d\n",ans[i]);
    return 0;