提出 #73720660

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ソースコード 拡げる

#include<bits/stdc++.h>
#define LL long long
#define PII pair<int, int>
#define PLI pair<LL, int>
#define PLL pair<LL, LL>
using namespace std;
const int N = 2e5, inf = 1e9;
vector<vector<int> > g;
bool vis[N + 5];
int n, siz[N + 5], mimx, tsiz, rt;
void get_siz(int u = rt, int p = 0) {
	tsiz++;
	for (auto v : g[u]) {
		if (vis[v] || v == p) continue;
		get_siz(v, u);
	}
}
void get_rt(int u, int p = 0) {
	siz[u] = 1;
	int ret = 0;
	for (auto v : g[u]) {
		if (vis[v] || v == p) continue;
		get_rt(v, u);
		siz[u] += siz[v];
		ret = max(ret, siz[v]);
	}
	ret = max(ret, tsiz - siz[u]);
	if (ret < mimx) {
		rt = u;
		mimx = ret;
	}
}
int getd(int u, int p, int d = 1) {
	int ret = 0, cnt = 0;
	for (auto v : g[u]) if (v != p) cnt++;
	if (cnt >= 2) ret = d;
	if (cnt <= 2) return ret;
	for (auto v : g[u]) if (!vis[v] && v != p) {
		ret = max(ret, getd(v, u, d + 1));
	}
	return ret;
}
int ans = 0;
void calc(int u) {
	int cnt = 0, mx = 0;
	for (auto v : g[u]) cnt++;
	if (cnt >= 2) ans = max(ans, 1);
	for (auto v : g[u]) if (!vis[v]) {
		int ret = getd(v, u);
		if (cnt >= 3) ans = max(ans, ret + 1);
		if (cnt >= 4) {
			ans = max(ans, mx + 1 + ret);
			mx = max(mx, ret);
		}
	}
}
void devide() {
	vis[rt] = 1;
	calc(rt);
	for (auto v : g[rt]) {
		if (vis[v]) continue;
		mimx = inf;
		get_rt(v);
		tsiz = 0;
		get_siz();
		devide();
	}
}

inline void solve() {
	cin >> n; ans = 0;
	g.clear(); g.resize(n + 1);
	memset(vis, 0, sizeof vis);
	for (int i = 1; i < n; i++) {
		int u, v; cin >> u >> v;
		g[u].push_back(v);
		g[v].push_back(u);
	}
	mimx = inf;
	get_rt(1);
	tsiz = 0;
	get_siz();
	devide();
	cout << ans << "\n";
}
signed main() {
	ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
	int t = 1;
	cin >> t;
	while (t--) solve();
	return 0;
} 

提出情報

コンパイルエラー

./Main.cpp: In function 'void calc(int)':
./Main.cpp:46:19: warning: unused variable 'v' [-Wunused-variable]
   46 |         for (auto v : g[u]) cnt++;
      |                   ^

ジャッジ結果