Submission #138140

#	Time	Username	Problem	Language	Result	Execution time	Memory
138140		Mahmoud_Adel	Mergers (JOI19_mergers)	C++14	100 / 100	1517 ms	127208 KiB

mergers

#include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
typedef long long ll;
const int N = 5e5+5;
int n, m, ans, cur, s[N], dep[N], sp[N][21], sub[N], ret[N], mark[N], deg[N];
vector<int> adj[N], vec[N];
void pre(int u, int p)
{
	sub[u] = 1;
	dep[u] = dep[p]+1;
	sp[u][0] = p;
	for(int i=1; i<21; i++) sp[u][i] = sp[sp[u][i-1]][i-1];
	for(int v : adj[u]) if(v != p) pre(v, u), sub[u] += sub[v];	
}
int equate(int u, int v)
{
	int c = dep[u]-dep[v];
	for(int i=0; i<21; i++) if(c & (1<<i)) u = sp[u][i];
	return u;
}
int LCA(int u, int v)
{
	if(dep[u] < dep[v]) swap(u, v);
	u = equate(u, v);
	if(u == v) return u;
	for(int i=20; i>=0; i--) if(sp[u][i] != sp[v][i]) u = sp[u][i], v = sp[v][i];
	return sp[u][0];
}
void calc(int u, int p)
{
	for(auto v : adj[u]) if(v != p) calc(v, u), ret[u] += ret[v];
	if(ret[u] == sub[u]) mark[u] = 1;
}
void DFS(int u, int p, int last)
{
	for(int v : adj[u]) if(p != v)
	{
		if(mark[v] && mark[last]) deg[v]++, deg[last]++, DFS(v, u, v);
		else DFS(v, u, last);
	}
}
int main()
{
	scanf("%d %d", &n, &m);
	for(int i=1, a, b; i<n; i++) scanf("%d %d", &a, &b),
	adj[a].push_back(b), adj[b].push_back(a);
	for(int i=1; i<=n; i++) scanf("%d", &s[i]), vec[s[i]].push_back(i);
	pre(1, 0);
	for(int i=1; i<=m; i++) 
	{
		if(vec[i].empty()) continue;
		int node = vec[i][0];
		for(auto u : vec[i]) node = LCA(node, u);
		ret[node] += (int)vec[i].size();
		assert(node);
	}
	calc(1, 0);
	DFS(1, 0, 1);
	for(int i=1; i<=n; i++) ans += (deg[i]==1);
	cout << (ans+1)/2 << endl;
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:46:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~~
mergers.cpp:48:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1, a, b; i<n; i++) scanf("%d %d", &a, &b),
                               ~~~~~~~~~~~~~~~~~~~~~~~~
  adj[a].push_back(b), adj[b].push_back(a);
  ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
mergers.cpp:49:44: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1; i<=n; i++) scanf("%d", &s[i]), vec[s[i]].push_back(i);
                          ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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