#include<bits/stdc++.h>
#define ll long long
#define MP make_pair
#define PII pair<int,int>
#define PB push_back
using namespace std;
constexpr int N = 1e6 + 10;
int n, T, p[N];
vector <int> g[N];
void dfs (int u, int fa, int col)
{
	for (int i = 0; i < (int) g[u].size (); i++)
	{
		int v = g[u][i];
		if (v == fa) continue;
		dfs (v, u, col ^ 1);
	}
}
int main ()
{
	cin >> T;
	while (T--)
	{
		for (int i = 0; i <= n; i++) g[i].clear ();
		cin >> n;
		for (int i = 1; i < n; i++) {int u, v; cin >> u >> v; g[u].PB (v), g[v].PB (u);}
		dfs (1, 0, 0);
	}
	return 0;
}

这个代码在跑n=80000的样例的时候玄学re了

麻烦dalao救一下