#include "bits/stdc++.h"
using namespace std;
using ll = long long;
#define MAXN 200005
#define MAXR 25005
#define INF (long long)1e18
#define BLOCK 450
int n, r, q;
vector<int> region(MAXN);
vector<vector<int>> adj(MAXN);
int timer = 1;
int tin[MAXN], tout[MAXN];
vector<vector<int>> sorted(MAXR); // sorted[r] stores the nodes from region r in sorted order of {tin, tout}
vector<int> ind(MAXR);
vector<vector<int>> par(BLOCK, vector<int>(MAXR));
vector<vector<int>> child(BLOCK, vector<int>(MAXR));
vector<int> largeRegions;
void dfs(int curr) {
// cout << "curr: " << curr << endl;
tin[curr] = timer++;
sorted[region[curr]].push_back(curr);
for (auto next: adj[curr]) {
dfs(next);
}
tout[curr] = timer - 1;
}
// Get answer for (a, b), sz[a] > BLOCK, sz[b] <= BLOCK
void genPar(int curr, int originalReg, int cnt) {
par[ind[originalReg]][region[curr]] += cnt;
int newCount = cnt + (region[curr] == originalReg);
for(auto child : adj[curr]) {
genPar(child, originalReg, newCount);
}
}
// Get answer for (a, b), sz[a] <= BLOCK, sz[b] > BLOCK
int genChild(int curr, int originalReg) {
int sub = (region[curr] == originalReg);
for(auto child : adj[curr]) {
sub += genChild(child, originalReg);
}
child[ind[originalReg]][region[curr]] += sub;
return sub;
}
int getAns(int reg1, int reg2) {
int l = 0, r = 0;
int ans = 0;
stack<int> st;
while (l < sorted[reg1].size() || r < sorted[reg2].size()) {
if ((l < sorted[reg1].size()) && (r == sorted[reg2].size() || tin[sorted[reg1][l]] < tin[sorted[reg2][r]])) {
while (!st.empty() && !isAnc(st.top(), sorted[reg1][l])) {
st.pop();
}
st.push(sorted[reg1][l]);
l++;
} else {
while (!st.empty() && !isAnc(st.top(), sorted[reg2][r])) {
st.pop();
}
ans += st.size();
r++;
}
}
return ans;
}
bool isAnc(int a, int b) {
return tin[a] <= tin[b] && tout[b] <= tout[a];
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
// freopen("", "r", stdin);
// freopen("", "w", stdout);
int n, r, q; cin >> n >> r >> q;
cin >> region[1];
for (int i = 2; i <= n; i++) {
int s; cin >> s >> region[i];
adj[s].push_back(i);
}
dfs(1);
int idx = 0;
for (int i = 1; i <= r; i++) {
if (sorted[i].size() > BLOCK) {
largeRegions.push_back(i);
ind[i] = idx++;
}
}
for (auto a : largeRegions) {
genPar(1, a, 0);
genChild(1, a);
}
for (int i = 0; i < q; i++) {
int a, b; cin >> a >> b;
if (sorted[a].size() <= BLOCK && sorted[b].size() <= BLOCK) {
cout << getAns(a, b) << endl;
continue;
}
if (sorted[a].size() > BLOCK) {
cout << par[ind[a]][b] << endl;
} else {
cout << child[ind[b]][a] << endl;
}
}
}
Compilation message
regions.cpp: In function 'int getAns(int, int)':
regions.cpp:62:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
62 | while (l < sorted[reg1].size() || r < sorted[reg2].size()) {
| ~~^~~~~~~~~~~~~~~~~~~~~
regions.cpp:62:41: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
62 | while (l < sorted[reg1].size() || r < sorted[reg2].size()) {
| ~~^~~~~~~~~~~~~~~~~~~~~
regions.cpp:63:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
63 | if ((l < sorted[reg1].size()) && (r == sorted[reg2].size() || tin[sorted[reg1][l]] < tin[sorted[reg2][r]])) {
| ~~^~~~~~~~~~~~~~~~~~~~~
regions.cpp:63:45: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
63 | if ((l < sorted[reg1].size()) && (r == sorted[reg2].size() || tin[sorted[reg1][l]] < tin[sorted[reg2][r]])) {
| ~~^~~~~~~~~~~~~~~~~~~~~~
regions.cpp:64:36: error: 'isAnc' was not declared in this scope
64 | while (!st.empty() && !isAnc(st.top(), sorted[reg1][l])) {
| ^~~~~
regions.cpp:71:36: error: 'isAnc' was not declared in this scope
71 | while (!st.empty() && !isAnc(st.top(), sorted[reg2][r])) {
| ^~~~~
