Submission #1146413

#	Time	Username	Problem	Language	Result	Execution time	Memory
1146413		SmuggingSpun	Mergers (JOI19_mergers)	C++20	0 / 100	39 ms	19900 KiB

mergers

#include<bits/stdc++.h>
#define taskname "B"
using namespace std;
const int lim = 5e5 + 5;
int n, k, p[lim], vertex[lim], d[lim];
vector<int>g[lim];
int find_set(int N){
	while(N != p[N]){
		N = p[N] = p[p[N]];
	}
	return N;
}
void merge(int a, int b){
	p[find_set(a)] = find_set(b);
}
int main(){
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	if(fopen(taskname".inp", "r")){
		freopen(taskname".inp", "r", stdin);
	}
	cin >> n >> k;
	for(int i = 1; i < n; i++){
		int u, v;
		cin >> u >> v;
		g[u].emplace_back(v);
		g[v].emplace_back(u);
	}
	memset(vertex, -1, sizeof(vertex));
	iota(p + 1, p + n + 1, 1);
	for(int i = 1; i <= n; i++){
		int x;
		cin >> x;
		if(vertex[x] == -1){
			vertex[x] = x;
		}
		else{
			merge(vertex[x], i);
		}
	}
	int cnt = 0;
	memset(d, 0, sizeof(d));
	for(int i = 1; i <= n; i++){
		for(int& j : g[i]){
			if(find_set(i) != find_set(j)){
				if(d[find_set(i)]++ == 0){
					cnt++;
				}
				else if(d[find_set(i)] == 2){
					cnt--;
				}
			}
		}
	}
	cout << ((cnt + 1) >> 1);
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:19:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |                 freopen(taskname".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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