Submission #934178

#	Time	Username	Problem	Language	Result	Execution time	Memory
934178		beepbeepsheep	Mergers (JOI19_mergers)	C++17	0 / 100	52 ms	49860 KiB

mergers

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;

typedef tree<long long, null_type, less_equal<>,
        rb_tree_tag, tree_order_statistics_node_update>
        ordered_set;
        
#define ll long long
#define ii pair<ll,ll>
#define iii tuple<ll,ll,ll>

#ifndef DEBUG
#define cerr if (0) cerr
#define endl '\n'
#endif

const ll inf=1e15;
const ll maxn=5e5+5;
const ll mod=1e9+7;

mt19937 rng(69);

vector<ll> adj[maxn];
vector<ll> type[maxn];
ll h[maxn];
ll dp[maxn];
ll pre[maxn],post[maxn],pref[maxn];
ll TIME,cnt;
vector<ll> check;
void dfs(ll x, ll p=0){
	pre[x]=++TIME;
	dp[x]=h[x];
	for (auto u:adj[x]){
		if (u==p) continue;
		dfs(u,x);
		dp[x]^=dp[u];
	}
	post[x]=TIME;
	cerr<<dp[x]<<' '<<x<<endl;
	if (x!=1 && dp[x]==0){
		pref[pre[x]]++;
		pref[post[x]+1]--;
		check.emplace_back(x);
		cnt++;
	}
}
int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	ll n,k,a,b;
	cin>>n>>k;
	for (int i=1;i<n;i++){
		cin>>a>>b;
		adj[a].emplace_back(b);
		adj[b].emplace_back(a);
	}
	for (int i=1;i<=n;i++){
		cin>>a;
		type[a].emplace_back(i);
	}
	for (int i=1;i<=k;i++){
		ll tot=0;
		for (int j=0;j<type[i].size()-1;j++){
			h[type[i][j]]=rng();
			tot^=h[type[i][j]];
		}
		h[type[i].back()]=tot;
	}
	dfs(1);
	for (int i=1;i<maxn;i++) pref[i]+=pref[i-1];
	ll ans=0;
	for (auto u:check){
		ll res=pref[post[u]]-pref[pre[u]-1]; //number of bad edges in subtree
		if (res==1 || res==cnt) ans++;
	}
	cout<<(ans+1)/2;
	return 0;
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:66:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   66 |   for (int j=0;j<type[i].size()-1;j++){
      |                ~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 24
• Subtask 3: 0 / 14
• Subtask 4: 0 / 22
• Subtask 5: 0 / 30