Submission #332887

#	Time	Username	Problem	Language	Result	Execution time	Memory
332887		Kenzo_1114	Mergers (JOI19_mergers)	C++17	0 / 100	87 ms	42724 KiB

mergers

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 500010;

int n, k, qtt[MAXN], in[MAXN];

int par[MAXN], depth[MAXN], need[MAXN], have[MAXN];
set<int> s[MAXN];
set<int> :: iterator it;

bool marc[MAXN];
vector<int> graph[MAXN];
map<pair<int, int>, bool> specialEdge;

void Special(int u, int v)
{
	specialEdge[make_pair(u, v)] = true;
	specialEdge[make_pair(v, u)] = true;
}

int find(int v)
{
	return (v == par[v]) ? v : par[v] = find(par[v]);
}

void join(int a, int b)
{
	a = find(a), b = find(b);
	if(a == b)	return;
	if(depth[a] > depth[b])	swap(a, b);

	par[a] = b;
	have[b] += have[a];

	for(it = s[a].begin(); it != s[a].end(); it++)
		if(s[b].find(*it) == s[b].end()) need[b] += qtt[*it], s[b].insert(*it);	
	
	if(depth[a] == depth[b])	depth[b]++;
}

int main ()
{
	scanf("%d %d", &n, &k);

	for(int i = 0, u, v; i < n - 1; i++)
	{
		scanf("%d %d", &u, &v);
		graph[u].push_back(v);
		graph[v].push_back(u);
		in[u]++, in[v]++;
	}

	queue<int> q;
	for(int i = 1, g; i <= n; i++)	
	{
		scanf("%d", &g);	qtt[g]++;
		if(in[i] == 1)	q.push(i), marc[i] = true;
	}

	for(int i = 1; i <= n; i++)
	{
		par[i] = i;
		need[i] = qtt[i];
		have[i] = 1;
	}

	while(!q.empty())
	{
		int v = q.front(); q.pop();

		for(int i = 0; i < (int) graph[v].size(); i++)
		{
			int u = graph[v][i];
			if(marc[u])	continue;
			
			if(have[v] == need[v])	Special(u, v);
			q.push(u);
			marc[u] = true;
			join(v, u);
		}
	}

	for(int i = 1; i <= n; i++)
	{
		marc[i] = false;
		if(in[i] == 1)	q.push(i), marc[i] = true;
	}

	int ans = 0;
	while(!q.empty())
	{
		int v = q.front(); q.pop();

		for(int i = 0; i < (int) graph[v].size(); i++)
		{
			int u = graph[v][i];
			if(marc[u])	continue;
			
			if(specialEdge[make_pair(u, v)]){	ans++; continue;	}
			q.push(u);
			marc[u] = true;
			join(v, u);
		}
	}

	printf("%d\n", (ans + 1) >> 1);
}

/*

5 4
1 2
2 3
3 4
3 5
1
2
1
3
4

*/

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:43:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   43 |  scanf("%d %d", &n, &k);
      |  ~~~~~^~~~~~~~~~~~~~~~~
mergers.cpp:47:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   47 |   scanf("%d %d", &u, &v);
      |   ~~~~~^~~~~~~~~~~~~~~~~
mergers.cpp:56:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   56 |   scanf("%d", &g); qtt[g]++;
      |   ~~~~~^~~~~~~~~~

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