Submission #1277238

#	Time	Username	Problem	Language	Result	Execution time	Memory
1277238		mingga	Cat Exercise (JOI23_ho_t4)	C++20	100 / 100	134 ms	44904 KiB

Main

// Author: caption_mingle
#include "bits/stdc++.h"

using namespace std;

#define ln "\n"
#define pb push_back
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define ll long long
const int mod = 1e9 + 7;
const int inf = 2e9;
const int N = 2e5 + 7;
int n, a[N], up[N][20], h[N];
int par[N], sz[N], mx[N];
ll f[N];

vector<int> g[N];

void dfs(int u, int p) {
	for(int i = 1; i < 20; i++) {
		up[u][i] = up[up[u][i - 1]][i - 1];
	}
	for(int v : g[u]) {
		if(v == p) continue;
		h[v] = h[u] + 1;
		up[v][0] = u;
		dfs(v, u);
	}
}

int lca(int u, int v) {
	if(h[u] < h[v]) swap(u, v);
	int k = h[u] - h[v];
	for(int i = 0; (1 << i) <= k; i++) {
		if(k >> i & 1) u = up[u][i];
	}
	if(u == v) return u;
	for(int i = 19; i >= 0; i--) {
		if(up[u][i] != up[v][i]) {
			u = up[u][i];
			v = up[v][i];
		}
	}
	return up[u][0];
}

int dist(int u, int v) {
	return h[u] + h[v] - 2 * h[lca(u, v)];
}

int find(int u) {
	return u == par[u] ? u : par[u] = find(par[u]);
}

void join(int u, int v) {
	u = find(u), v = find(v);
	if(u == v) return;
	if(sz[u] < sz[v]) swap(u, v);
	sz[u] += sz[v];
	par[v] = u;
	mx[u] = max(mx[u], mx[v]);
}

signed main() {
	cin.tie(0) -> sync_with_stdio(0);
	#define task ""
	if(fopen(task ".INP", "r")) {
		freopen(task ".INP", "r", stdin);
		freopen(task ".OUT", "w", stdout);
	}
	cin >> n;
	for(int i = 1; i <= n; i++) cin >> a[i];
	for(int i = 1; i < n; i++) {
		int u, v; cin >> u >> v;
		u = a[u], v = a[v];
		g[u].pb(v);
		g[v].pb(u);
	}
	dfs(1, 0);
	for(int i = 1; i <= n; i++) {
		sz[i] = 1;
		par[i] = mx[i] = i;
	}
	for(int i = 1; i <= n; i++) {
		for(int v : g[i]) {
			v = mx[find(v)];
			if(v < i) {
				f[i] = max(f[i], f[v] + 1ll * dist(i, mx[v]));
				join(i, v);
			}
		}
	}
	cout << f[n] << ln;
    cerr << "\nTime: " << clock() * 1000 / CLOCKS_PER_SEC;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:71:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   71 |                 freopen(task ".INP", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:72:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   72 |                 freopen(task ".OUT", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• 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