广东工业大学新生赛决赛F题

// by BNU_LZM
#include
#include
#include
#include
using namespace std;

const int maxn = 100000+5;

struct Edge
{
	int u, v, d;
	Edge(int u, int v, int d) : u(u), v(v), d(d) {}
};

vector edges;
vector G[maxn];

int n, dep[maxn], dis[maxn], f[maxn];

void dfs(int u, int d)
{
	dep[u] = d;
	for(int i = 0; i < G[u].size(); i++)
	{
		Edge &e = edges[G[u][i]];
		int v = e.v;
		if(v == f[u]) continue;
		dis[v] = e.d;
		f[v] = u;
		dfs(v, d+1);
	}
}

bool solve(int a, int b)
{
	vector aa;
	while(a != b)
	{
		if(aa.size() >= 50) return true;
		if(dep[a] > dep[b])
		{
			aa.push_back(dis[a]);
			a = f[a];
		}
		else
		{
			aa.push_back(dis[b]);
			b = f[b];
		}
	}
	if(aa.size() < 3) return false;
	sort(aa.begin(), aa.end());
	for(int i = 0; i < aa.size()-2; i++)
	{
		if(aa[i]+aa[i+1] > aa[i+2]) return true;
	}
	return false;
}

int main()
{
	freopen("in.txt", "r", stdin);
	int T;
	scanf("%d", &T);
	while(T--)
	{
		edges.clear();
		for(int i = 1; i <= n; i++) G[i].clear();
		scanf("%d", &n);
		for(int i = 1; i < n; i++)
		{
			int u, v, d;
			scanf("%d%d%d", &u, &v, &d);
			edges.push_back(Edge(u, v, d));
			G[u].push_back(edges.size()-1);
			edges.push_back(Edge(v, u, d));
			G[v].push_back(edges.size()-1);
		}
		memset(f, -1, sizeof(f));
		dfs(1, 0);
		int m;
		scanf("%d", &m);
		for(int i = 1; i <= m; i++)
		{
			int a, b;
			scanf("%d%d", &a, &b);
			if(solve(a, b)) printf("Yes\n");
			else printf("No\n");
		}
	}
	return 0;
}