Submission #416568

#	Time	Username	Problem	Language	Result	Execution time	Memory
416568		amirmohammad_nezami	Mergers (JOI19_mergers)	C++14	100 / 100	1270 ms	144572 KiB

mergers

//                                                          In the name of God 
#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define lc 2 * v
#define rc 2 * v + 1
#define mid (s + e) / 2
#define _sz(e) (int)e.size()
#define _all(e) e.begin() , e.end()
#define _lcm(a , b) (1ll * a * b) / __gcd(a , b)
#define ll long long
#define int long long
#define ld long double
#define pii pair <int , int>
#define pcc pair <char , char>
#define pll pair <long long , long long>
#define piii pair <int , pair <int , int>>
#define FAST ios::sync_with_stdio(0);cin.tie(0)
#pragma GCC optimize("Ofast")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,avmini,avmini2")

const int maxn = 5e5 + 10 , N = 2e6 + 10 , SQ = 320 , base = 800287 , mod = 1e9 + 7 , INF = 1e18 + 10 , lg = 22;
const ld eps = 1e-4;

int n , k , s[maxn] , mn_st[maxn] , mx_ft[maxn], st[maxn] , ft[maxn] , tme;
int mx_sub[maxn] , mn_sub[maxn] , mark[maxn] , cnt[maxn];
vector <int> edges[maxn];

void dfs1(int v , int p = -1) {
	st[v] = tme++;
	if(mn_st[s[v]] == -1) {
		mn_st[s[v]] = st[v];
	}	

	for (auto u : edges[v]) {
		if(u != p) {
			dfs1(u , v);
		}
	}
	ft[v] = tme;
	mx_ft[s[v]] = ft[v];
}

void dfs2(int v , int p = -1) {
	mn_sub[v] = mn_st[s[v]] , mx_sub[v] = mx_ft[s[v]];
	for (auto u : edges[v]) {
		if(u != p) {
			dfs2(u , v);
			mn_sub[v] = min(mn_sub[v] , mn_sub[u]);
			mx_sub[v] = max(mx_sub[v] , mx_sub[u]);
		}
	}

	if(p != -1 && mn_sub[v] == st[v] && mx_sub[v] == ft[v]) {
		mark[v] = 1;
	}
}

void dfs3(int v , int p = -1 , int root = 0) {
	for (auto u : edges[v]) {
		if(u != p) {
			if(mark[u]) {
				cnt[root]++ , cnt[u]++;
				dfs3(u , v , u);
			}
			else {
				dfs3(u , v , root);
			}
		}
	}
}

int32_t main() {	
	FAST;
	cin >> n >> k;
	for (int i = 0; i < n - 1; ++i) {
		int x , y; cin >> x >> y;
		x-- , y--;
		edges[x].PB(y);
		edges[y].PB(x);
	}
	for (int i = 0; i < n; ++i) {
		cin >> s[i]; s[i]--;
	}
	for (int i = 0; i < k; ++i) {
		mn_st[i] = -1;
	}

	dfs1(0);
	dfs2(0);
	dfs3(0);
	
	int ans = 0;
	for (int i = 0; i < n; ++i) {
		ans += (cnt[i] == 1);
	}
	cout << (ans + 1) / 2 << '\n';
} 

//  Mistakes:
//  * Read the problem carefully.
//  * Check maxn.
//  * Overflows.

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