Submission #333160

#	Time	Username	Problem	Language	Result	Execution time	Memory
333160		ly20	Mergers (JOI19_mergers)	C++17	0 / 100	117 ms	57572 KiB

mergers

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

int n, k, qtt[MAXN], g[MAXN], in[2][MAXN];

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

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;
}

void dfs(int v, int p)
{
	for(int i = 0; i < (int) graph[v].size(); i++)
	{
		int u = graph[v][i];
		if(u != p)	dfs(u, v);
	}
}

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[0][u]++, in[0][v]++;
	}

	queue<int> q;
	for(int i = 1; i <= n; i++)	
	{
		scanf("%d", &g[i]);	qtt[g[i]]++;
		in[1][i] = in[0][i];
		if(in[0][i] == 1)	q.push(i);
	}

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

	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(in[0][u] >= 1 && have[find(v)] == need[find(v)])	Special(u, v);
			if(in[0][u] >= 1)	join(v, u);
          	in[0][u]--;
			if(in[0][u] == 1)	in[0][u] = 0,	q.push(u);
		}
	}

	for(int i = 1; i <= n; i++)	
		if(in[1][i] == 1)	q.push(i);

	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];
			in[1][u]--;

			if(specialEdge[make_pair(u, v)]){	ans++; in[1][u] = 0; continue;	}
			if(in[1][u] == 1)	in[1][u] = 0, q.push(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:51:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |  scanf("%d %d", &n, &k);
      |  ~~~~~^~~~~~~~~~~~~~~~~
mergers.cpp:55:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   55 |   scanf("%d %d", &u, &v);
      |   ~~~~~^~~~~~~~~~~~~~~~~
mergers.cpp:64:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |   scanf("%d", &g[i]); qtt[g[i]]++;
      |   ~~~~~^~~~~~~~~~~~~

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