Submission #854924

#	Time	Username	Problem	Language	Result	Execution time	Memory
854924		rxlfd314	Regions (IOI09_regions)	C++17	100 / 100	3523 ms	127692 KiB

regions

#include <bits/stdc++.h>
using namespace std;
 
constexpr int mxN = 200069, BSZ = 125; // wtf 125 works??? this is so cringe
int N, R, Q, H[mxN], rgnOrd[mxN>>3], revOrd[mxN>>3];
vector<int> adj[mxN], rgnLst[mxN>>3], rgnLst2[mxN>>3];
 
int timer, tin[mxN], tout[mxN];
int tdall[BSZ][BSZ], td[mxN][BSZ];
void dfs(int f) {
	tin[f] = timer++;
	for (int i = 0; i < min(R, BSZ) && revOrd[H[f]] < BSZ; i++) {
		tdall[revOrd[H[f]]][i] += td[f][i];
	}
	for (int nf : adj[f]) {
		for (int i = 0; i < min(R, BSZ); i++) {
			td[nf][i] = td[f][i] + (rgnOrd[i] == H[f]);
		}
		dfs(nf);
	}
	tout[f] = timer-1;
}
 
signed main() {
	scanf("%d%d%d%d", &N, &R, &Q, &H[0]);
	rgnLst[--H[0]].push_back(0);
	for (int i = 1, p; i < N; i++) {
		scanf("%d%d", &p, &H[i]);
		adj[--p].push_back(i);
		rgnLst[--H[i]].push_back(i);
	}
 
	iota(rgnOrd, rgnOrd+R, 0);
	sort(rgnOrd, rgnOrd+R, [&](const int &a, const int &b) {
		return rgnLst[a].size() > rgnLst[b].size();					 
	});
	for (int i = 0; i < R; i++) {
		revOrd[rgnOrd[i]] = i;
	}
	dfs(0);
	for (int i = 0; i < R; i++) {
		for (int j : rgnLst[i]) {
			rgnLst2[i].push_back(tin[j]);
		}
		sort(rgnLst2[i].begin(), rgnLst2[i].end());
	}
 
	for (int a, b, ans; Q--; ) {
		scanf("%d%d", &a, &b);
		a--, b--;
		ans = 0;
		if (revOrd[a] < BSZ && revOrd[b] < BSZ) {
			ans = tdall[revOrd[b]][revOrd[a]];
		} else if (revOrd[a] < BSZ) {
			for (int i : rgnLst[b]) {
				ans += td[i][revOrd[a]];
			}
		} else {
			for (int i : rgnLst[a]) {
				ans += upper_bound(rgnLst2[b].begin(), rgnLst2[b].end(), tout[i]) - lower_bound(rgnLst2[b].begin(), rgnLst2[b].end(), tin[i]);
			}
		}
		printf("%d\n", ans);
      	fflush(stdout);
	}
}

Compilation message (stderr)

regions.cpp: In function 'int main()':
regions.cpp:25:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   25 |  scanf("%d%d%d%d", &N, &R, &Q, &H[0]);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
regions.cpp:28:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |   scanf("%d%d", &p, &H[i]);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~
regions.cpp:49:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   49 |   scanf("%d%d", &a, &b);
      |   ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 15 / 15
• Subtask 2: 85 / 85