Submission #1254356

#	Time	Username	Problem	Language	Result	Execution time	Memory
1254356		thdh__	Capital City (JOI20_capital_city)	C++20	100 / 100	651 ms	38608 KiB

capital_city

#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define eb emplace_back
#define pu push
#define ins insert
#define fi first
#define se second
#define all(a) a.begin(),a.end()
#define bruh ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fu(x,a,b) for (auto x=a;x<=b;x++)
#define fd(x,a,b) for (auto x=a;x>=b;x--)

using namespace std;
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());

/*
Competitive Programming notes that I need to study & fix my dumbass self:

1. Coding:
- Always be sure to check the memory of arrays (maybe use vectors), for loops
- Always try to maximize the memory if possible, even if you are going for subtasks
- Do not exploit #define int long long, it will kill you

2. Stress: 
- Always try generating big testcases and try if they run

3. Time management:
- Don't overcommit or undercommit, always spend a certain amount of time to think a problem, don't just look at it and say I'm fucked
- Do not spend too much time coding brute-force solutions, they should be easily-codable solutions that don't take up too much time

Time management schedule:
Offline / LAH days (4 problems - 3h):
15' thinking of solution / idea
1. no idea: skip
2. yes idea: continue thinking for <= 15'

+ implementing: <= 20'
+ brute-force: <= 5'
+ test generator: <= 5'

I hate offline because I am dumb
*/

typedef pair<int, int> ii;
const int N = 2e5+5;
const int B = 750;
const int mod = 1e9+7;
const int inf = 2e9;
using cd = complex<double>;
const long double PI = acos(-1);
int power(int a,int b) {ll x = 1;if (a >= mod) a%=mod; while (b) {if (b & 1) x = x*a % mod;a = a*a % mod;b>>=1;}return x;} 

int n,k;
vector<int> adj[N];
int a[N], sum[N];
int ans = inf;

int sz[N];
bool vis[N];
vector<int> ch[N];
bool check[N], chosen[N], go[N];
int par[N];
int stk[N], id = 0;

void predfs(int u, int p) 
{
	sz[u] = 1;
	for (auto v : adj[u]) 
	{
		if (v == p || vis[v]) continue;
		predfs(v, u);
		sz[u] += sz[v];
	}
}

int centroid(int u, int p, int siz) 
{
	for (auto v : adj[u]) 
	{
		if (v == p || vis[v]) continue;
		if (sz[v]*2 > siz) return centroid(v, u, siz);
	}
	return u;
}

void reset() 
{
	while (id) 
	{
		--id;
		check[stk[id]] = chosen[a[stk[id]]] = go[stk[id]] = 0;
	}
}

void dfs(int u, int p) 
{
	go[u] = 1;
	stk[id++] = u;
	par[u] = p;
	for (auto v : adj[u]) 
	{
		if (v == p || vis[v]) continue;
		dfs(v, u); 
	}
}

void decomp(int u)
{
	predfs(u, 0);
	int c = centroid(u, 0, sz[u]);
	// dfs(c, 0);
	// cout<<"Centroid = "<<c<<endl;
	dfs(c, 0);
	bool can = 1;
	queue<int> q;
	for (auto i : ch[a[c]]) 
	{
		if (!go[i])
		{
			can = 0; break;
		}
		q.push(i), check[i] = 1;
	}
	int cnt = 0;
	while (can && !q.empty()) 
	{
		int v = q.front();
		// cout<<v<<" ";
		q.pop();
		while (can && par[v] && !check[par[v]]) 
		{
			v = par[v];
			check[v] = 1;
			if (!chosen[a[v]]) 
			{
				chosen[a[v]] = 1;
				cnt++;
				// cout<<a[v]<<endl;
				for (auto i : ch[a[v]]) 
				{
					// cout<<i<<" ";
					if (!go[i]) 
					{
						can = 0;
						break;
					}
					q.push(i), check[i] = 1;
				}
				// cout<<endl;
			}
		}
	}
	// cout<<endl;
	if (can) ans = min(ans, cnt);
	reset();
	vis[c] = 1;
	for (auto v : adj[c]) 
	{
		if (vis[v]) continue;
		decomp(v);
	}
}

void solve()
{
	cin>>n>>k;
	for (int i = 1; i < n; i++) 
	{
		int u,v; cin>>u>>v;
		adj[u].pb(v); adj[v].pb(u);
	}
	for (int i = 1; i <= n; i++) cin>>a[i], ch[a[i]].pb(i);
	decomp(1);
	cout<<ans;
}

/*
Go through the mistakes you usually make and revise your code, for god's sake...
*/

signed main()
{
	bruh
	//freopen("input.inp","r",stdin);
	//freopen("output.inp","w",stdout);
	int t = 1;
	// cin>>t;
	while (t--)
	{
		solve();
		cout<<"\n";
	}
}

• Subtask 1: 1 / 1
• Subtask 2: 10 / 10
• Subtask 3: 30 / 30
• Subtask 4: 59 / 59