Codeforces Round #151 (Div. 2) E. Blood Cousins Return

鏈接

https://codeforces.com/contest/246/problem/E

題解

$dsu\ on\ tree$裸題，想一下怎麼暴力：直接遍歷子樹，每個深度維護一個$set$，查詢的時候去對應的深度求$set$的大小就行了
刪除的時候就直接去$set$裏$erase$

代碼

#include <bits/stdc++.h>
#define maxn 100010
#define maxe 200010
#define cl(x) memset(x,0,sizeof(x))
using namespace std;
struct Trie
{
    int trie[maxn*20][28], tot, tail[maxn*20];
    void clear()     //clear the arrays
    {
        for(int i=1;i<=tot;i++)cl(trie[i]), tail[i]=0;
        tot=1;
    }
    int insert(int *r, int len)     //insert a string into trie tree
    {
        auto pos=1;
        for(auto i=1;i<=len;i++)
            pos = trie[pos][r[i]] ? trie[pos][r[i]] : trie[pos][r[i]]=++tot;
        tail[pos]++;
        return pos;
    }
}trie;
struct Graph
{
    int etot, head[maxn], to[maxe], next[maxe], w[maxe];
    void clear(int N)
    {
        for(int i=1;i<=N;i++)head[i]=0;
        etot=0;
    }
    void adde(int a, int b, int c){to[++etot]=b;w[etot]=c;next[etot]=head[a];head[a]=etot;}
}G;
struct ShuLianPouFen
{
    int size[maxn], top[maxn], tid[maxn], tim, untid[maxn], deep[maxn], son[maxn], fa[maxn];
    void dfs1(Graph &G, int pos)
    {
        int p, v;
        size[pos]=1;
        for(p=G.head[pos];p;p=G.next[p])
        {
            if((v=G.to[p])==fa[pos])continue;
            fa[v]=pos;
            deep[v]=deep[pos]+1;
            dfs1(G,v);
            if(size[v]>size[son[pos]])son[pos]=v;
            size[pos]+=size[v];
        }
    }
    void dfs2(Graph &G, int pos, int tp)
    {
        int p, v;
        top[pos]=tp;
        tid[pos]=++tim;
        untid[tid[pos]]=pos;
        if(son[pos])dfs2(G,son[pos],tp);
        for(p=G.head[pos];p;p=G.next[p])
            if((v=G.to[p])!=fa[pos] and v!=son[pos])dfs2(G,v,v);
    }
    void run(Graph &G, int root)
    {
        tim=0;
        dfs1(G,root);
        dfs2(G,root,root);
    }
}SP;
int n, m, k[maxn], ans[maxn], col[maxn], forb, f[maxn];
vector<int> qlis[maxn];
set<int> s[maxn];
void force(int pos, int pre, int opt)
{
    if(opt==1)s[SP.deep[pos]].emplace(col[pos]);
    else s[SP.deep[pos]].erase(col[pos]);
    for(auto p=G.head[pos];p;p=G.next[p])
        if(G.to[p]!=pre and G.to[p]!=forb)
            force(G.to[p],pos,opt);
}
void dfs(int pos, int pre, int H)
{
    for(auto p=G.head[pos];p;p=G.next[p])
        if(G.to[p]!=pre and G.to[p]!=SP.son[pos])
            dfs(G.to[p],pos,0);
    if(SP.son[pos])dfs(SP.son[pos],pos,1);
    forb=SP.son[pos];
    force(pos,pre,1);
    for(auto q:qlis[pos])
    {
        if(SP.deep[pos]+k[q]<=n)ans[q]=s[SP.deep[pos]+k[q]].size();
    }
    if(H==0)forb=0, force(pos,pre,-1);
}
int main()
{
    char s[50];
    int r[50], i;
    scanf("%d",&n);
    trie.clear();
    for(i=1;i<=n;i++)
    {
        scanf("%s%d",s+1,f+i);
        if(f[i]==0)f[i]=n+1;
        G.adde(i,f[i],0), G.adde(f[i],i,0);
        auto len=strlen(s+1);
        for(int j=1;j<=len;j++)r[j]=s[j]-'a'+1;
        col[i]=trie.insert(r,len);
    }
    SP.run(G,n+1);
    scanf("%d",&m);
    for(i=1;i<=m;i++)
    {
        int v;
        scanf("%d%d",&v,k+i);
        qlis[v].emplace_back(i);
    }
    dfs(n+1,0,0);
    for(i=1;i<=m;i++)printf("%d\n",ans[i]);
    return 0;
}