Submission #517060

#	Time	Username	Problem	Language	Result	Execution time	Memory
517060		Yuisuyuno	Regions (IOI09_regions)	C++14	100 / 100	4387 ms	118504 KiB

regions

#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5+10;
bool vis[25001];
int n,r,q,cnt=1, a[maxn], st[maxn], en[maxn], B[maxn];
unordered_map<int,int> calc[25001];
vector<int> adj[maxn], v[25001];
void dfs(int s, int p = -1)
{
	st[s] = cnt++;
	for(auto u : adj[s])
		if(u!=p) dfs(u,s);
	en[s] = cnt-1;
}

int32_t main()
{
	cin >> n >> r >> q >> a[1];
	for(int i = 2; i <= n; i++)
	{
		int x; cin >> x >> a[i];
		adj[x].push_back(i);
	}
	int K = sqrt(n);
	dfs(1); for(int i = 1; i <= n; i++) B[st[i]]=i;
	for(int i = 1; i <= n; i++) v[a[B[i]]].push_back(st[B[i]]);
	for(int i = 1; i <= n; i++)
	{
		if(vis[a[B[i]]]) continue;
		if(v[a[B[i]]].size()<=K) continue;
		vis[a[B[i]]]=true;
		int pref[n+2]{0};
		for(auto u : v[a[B[i]]])
		{
			int l = st[B[u]], r = en[B[u]];
			pref[l]++, pref[r+1]--;
		}
		for(int j = 1; j <= n; j++)
			pref[j]+=pref[j-1], calc[a[B[j]]][a[B[i]]]+=pref[j];
	}
	while(q--)
	{
		int a, b, ans = 0; cin >> a >> b;
		if(v[a].size()<=K){
			for(auto u : v[a]){
				int l = st[B[u]], r = en[B[u]];
				auto itr = upper_bound(v[b].begin(), v[b].end(), r)-v[b].begin();
				auto itr2 = upper_bound(v[b].begin(), v[b].end(), l)-v[b].begin();
				if(itr) itr--, ans+=max((int)(itr-itr2)+1, 0);
			}
		}
		else ans = calc[b][a];
		cout << ans << endl;
	}
}

Compilation message (stderr)

regions.cpp: In function 'int32_t main()':
regions.cpp:30:23: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   30 |   if(v[a[B[i]]].size()<=K) continue;
      |      ~~~~~~~~~~~~~~~~~^~~
regions.cpp:44:17: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   44 |   if(v[a].size()<=K){
      |      ~~~~~~~~~~~^~~

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