Submission #1111865

#	Time	Username	Problem	Language	Result	Execution time	Memory
1111865		starchan	Cat Exercise (JOI23_ho_t4)	C++17	100 / 100	151 ms	63560 KiB

Main

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define in array<int, 2>
#define pb push_back
#define pob pop_back
#define fast() ios_base::sync_with_stdio(false); cin.tie(NULL)

const int MX = 2e5+5;
const int INF = 1e17;
const int LOGM = 18;

vector<int> adj[MX];

int par[LOGM][MX]; int dp[MX]; int dep[MX]; int tin[MX]; int tout[MX];

int T;

void dfs(int u, int p)
{
	tin[u] = ++T;
	par[0][u] = p;
	dep[u] = dep[p]+1;
	for(int v: adj[u])
	{
		if(v == p)
			continue;
		dfs(v, u);
	}
	tout[u] = T;
	return;
}

int dist(int u, int v)
{
	if(tin[u] > tin[v])
		swap(u, v);
	if(tout[u] >= tout[v])
		return dep[v]-dep[u];
	int s = u;
	for(int i = LOGM-1; i >= 0; i--)
	{
		if(tout[par[i][s]] < tout[v])
			s = par[i][s];
	}
	s = par[0][s];
	return dep[u]+dep[v]-2*dep[s];
}

vector<int> bst(MX);
vector<int> pa(MX, -1);

int leader(int u)
{
	if(pa[u] < 0)
		return u;
	return pa[u] = leader(pa[u]);
}

void merge(int u, int v)
{
	u = leader(u);
	v = leader(v);
	if(u == v)
		return;
	if(pa[u] < pa[v])
		swap(u, v);
	pa[v]+=pa[u];
	bst[v] = max(bst[v], bst[u]);
	pa[u] = v;
	return;
}

signed main()
{
	fast();
	int n; cin >> n;
	vector<int> p(n+1);
	for(int i = 1; i <= n; i++)
		cin >> p[i];
	for(int i = 1; i < n; i++)
	{
		int u, v; cin >> u >> v;
		u = p[u]; v = p[v];
		adj[u].pb(v); adj[v].pb(u);
	}
	par[0][0] = 0; dep[0] = 0; tout[0] = n+5;
	dfs(1, 0);
	for(int i = 1; i < LOGM; i++)
	{
		for(int u = 1; u <= n; u++)
			par[i][u] = par[i-1][par[i-1][u]];
	}
	for(int i = 1; i <= n; i++)
		bst[i] = i;
	for(int i = 1; i <= n; i++)
	{
		for(int j: adj[i])
		{
			if(j < i)
			{
				int w = bst[leader(j)];
				dp[i] = max(dp[i], dp[w]+dist(i, w));
				merge(i, j);
			}
		}
	}
	cout << dp[n] << "\n";
	return 0;
}	

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26