CF208E Blood Cousins(DSU，倍增)

倍增求出祖先，\(\text{DSU}\)统计

本来想用树剖求\(K\)祖，来条链复杂度就假了

#include <cstring>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <iostream>
#include <numeric>
#define R(a,b,c) for(register int a = (b); a <= (c); ++a)
#define nR(a,b,c) for(register int a = (b); a >= (c); --a)
#define Swap(a,b) ((a) ^= (b) ^= (a) ^= (b))
#define MP make_pair
#ifdef QWQ
#define D_e_Line printf("\n------\n")
#define D_e(x) cerr << (#x) << " " << x << endl
#define C_e(x) cout << (#x) << " " << x << endl
#define FileOpen() freopen("in.txt", "r", stdin)
#define FileSave() freopen("out.txt", "w", stdout)
#define Pause() system("pause")
#include <cassert>
#define PASS fprintf(stderr, "Passing [%s] in LINE %d\n",__FUNCTION__,__LINE__)
#else
#define D_e_Line
#define D_e(x)
#define C_e(x)
#define FileOpen()
#define FileSave()
#define Pause()
#define PASS
#endif
using namespace std;
struct FastIO {
	template<typename ATP> inline FastIO& operator >> (ATP &x) {
		x = 0; int sign = 1; char c;
		for(c = getchar(); c < '0' || c > '9'; c = getchar()) if(c == '-') sign = -1;
		while(c >= '0' && c <= '9') x = x * 10 + (c ^ '0'), c = getchar();
		if(sign == -1) x = -x;
		return *this;
	}
} io;
template<typename ATP> inline ATP Max(ATP x, ATP y) {
	return x > y ? x : y;
}
template<typename ATP> inline ATP Min(ATP x, ATP y) {
	return x < y ? x : y;
}
template<typename ATP> inline ATP Abs(ATP x) {
	return x < 0 ? -x : x;
}
#include <vector>
const int N = 1e5 + 7;
struct Edge {
	int nxt, pre;
} e[N];
int head[N], cntEdge;
inline void add(int u, int v) {
	e[++cntEdge] = (Edge){ head[u], v}, head[u] = cntEdge;
}
vector<pair<int, int>> q[N];
int dep[N], fa[N][19], siz[N], top[N], dfn[N], dfnIdx, rnk[N], son[N];
void DFS_First(int u, int father) {
	dep[u] = dep[father] + 1, fa[u][0] = father, siz[u] = 1;
	R(i,1,18){
		if(fa[u][i - 1]) fa[u][i] = fa[fa[u][i - 1]][i - 1];
		else break;
	}
	for(register int i = head[u]; i; i = e[i].nxt){
		int v = e[i].pre;
		DFS_First(v, u);
		siz[u] += siz[v];
		if(siz[v] > siz[son[u]]) son[u] = v;
	}
}
void DFS_Second(int u, int Tp) {
	top[u] = Tp, dfn[u] = ++dfnIdx, rnk[dfnIdx] = u;
	if(!son[u]) return;
	DFS_Second(son[u], Tp);
	for(register int i = head[u]; i; i = e[i].nxt){
		int v = e[i].pre;
		if(v != son[u]) DFS_Second(v, v);
	}
}
inline int Father(int u, int K) {
//	while(dep[u] - dep[top[u]] + 1 <= K){
//		K -= dep[u] - dep[top[u]] + 1;
//		u = fa[top[u]];
//	}
//	return rnk[dfn[u] - K];

	while(K){
		int now = 0;
		while((1 << (now + 1)) <= K) ++now;
		u = fa[u][now];
		K -= 1 << now;
	}
	return u;
}
int tot[N];
bool big[N];
void Add(int u) {
	++tot[dep[u]];
	for(register int i = head[u]; i; i = e[i].nxt){
		int v = e[i].pre;
		if(big[v]) continue;
		Add(v);
	}
}
void Del(int u) {
	--tot[dep[u]];
	for(register int i = head[u]; i; i = e[i].nxt){
		int v = e[i].pre;
		if(big[v]) continue;
		Del(v);
	}
}
int ans[N], n;
void DSU(int u, bool flag) {
	for(register int i = head[u]; i; i = e[i].nxt){
		int v = e[i].pre;
		if(v == son[u]) continue;
		DSU(v, 0);
	}
	if(son[u]) DSU(son[u], 1), big[son[u]] = true;
	Add(u);
	for(vector<pair<int, int>>::iterator it = q[u].begin(); it != q[u].end(); ++it){
		if(it->first + dep[u] <= n + 1){
			ans[it->second] = tot[it->first + dep[u]] - 1;
		}
	}
	big[son[u]] = false;
	if(!flag) Del(u);
}
int main() {
	int Q;
	io >> n;
	R(i,1,n){
		int fat;
		io >> fat;
		++fat;
		add(fat, i + 1);
	}
	DFS_First(1, 0);
	DFS_Second(1, 1);
//	while(1){
//		int x, K;
//		io >> x >> K;
//		++x;
//		cout << Father(x, K) - 1<< endl;
//	}
	io >> Q;
	R(i,1,Q){
		int x, K;
		io >> x >> K;
		++x;
		x = Father(x, K);
		if(x == 1){
			continue;
		}
//		D_e(x - 1);
		q[x].emplace_back(K, i);
	}
	DSU(1, 0);

	R(i,1,Q){
		printf("%d ", ans[i]);
	}
	return 0;
}
/*
6
0 1 1 0 4 4
7
1 1
1 2
2 1
2 2
4 1
5 1
6 1
*/
/*
6
0 1 2 3 4 5
5 1
*/