Codeforces246E Blood Cousins Return

dsu on tree

题目链接

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题目大意

解题思路

AC_Code

#include<bits/stdc++.h>
#define rep(i,a,n) for (int i=a;i<=n;i++)
#define per(i,n,a) for (int i=n;i>=a;i--)
#define pb push_back
#define fi first
#define se second
using namespace std;
const int N = 5e5 + 10;
struct Edge{
int nex , to;
}edge[N << 1];
int head
 , tot;
int a
 , dep
 , siz
 , hson
 , name
 , HH;
vector<pair<int , int>>Q
 , ans;
unordered_map<int , int>cnt
 , sum;
void add_edge(int u , int v)
{
edge[++ tot].nex = head[u];
edge[tot].to = v;
head[u] = tot;
}
void dfs(int u , int far)
{
siz[u] = 1;
dep[u] = dep[far] + 1;
for(int i = head[u] ; i ; i = edge[i].nex)
{
int v = edge[i].to;
if(v == far) continue ;
dfs(v , u);
siz[u] += siz[v];
if(siz[v] > siz[hson[u]]) hson[u] = v;
}
}
void calc(int u , int far , int val , int dep)
{
cnt[dep][name[u]] += val;
if(cnt[dep][name[u]] == 1 && val == 1) sum[dep] ++ ;
if(!cnt[dep][name[u]]) sum[dep] -- ;
for(int i = head[u] ; i ; i = edge[i].nex)
{
int v = edge[i].to;
if(v == far || v == HH) continue ;
calc(v , u , val , dep + 1);
}
}
void dsu(int u , int far, int op , int dep)
{
for(int i = head[u] ; i ; i = edge[i].nex)
{
int v = edge[i].to;
if(v == far || v == hson[u]) continue ;
dsu(v , u , 0 , dep + 1);
}
if(hson[u]) dsu(hson[u] , u , 1 , dep + 1) , HH = hson[u];
calc(u , far , 1 , dep);
for(auto i : Q[u])
{
int k = i.fi , id = i.se;
ans.pb(make_pair(id , sum[dep + k]));
}
HH = 0;
if(!op) calc(u , far , -1 , dep) , sum.clear();
}
map<string , int>vis;
signed main()
{
int n , q , tot = 0;
cin >> n;
rep(i , 1 , n)
{
string s;
int x;
cin >> s >> x;
if(!vis.count(s)) vis[s] = ++ tot;
name[i] = vis[s] , a[i] = x;
if(!x) continue ;
add_edge(i , x) , add_edge(x , i);
}
rep(i , 1 , n) if(!a[i]) dfs(i , 0);
cin >> q;
rep(i , 1 , q)
{
int a , b;
cin >> a >> b;
Q[a].pb(make_pair(b , i));
}
rep(i , 1 , n)
{
if(!a[i]) dsu(i , 0 , 0 , 1) ;
}
sort(ans.begin() , ans.end());
for(auto i : ans) cout << i.se << '\n';
return 0;
}