离线查找，蛋疼的是DFS居然要用栈....
#include <iostream> #include <set> #include <stack> using namespace std; const int maxn = 100005; struct Graph { int pnt[maxn*2], val[maxn*2], nxt[maxn*2]; int head[maxn], idx; bool sign[maxn]; void Init(int n) { memset(head, -1, 4 * (n + 1)); memset(sign, 0, n + 1); idx = 0; } void Addedge(int x, int y, int v) { pnt[idx] = y; val[idx] = v; nxt[idx] = head[x]; head[x] = idx++; pnt[idx] = x; val[idx] = v; nxt[idx] = head[y]; head[y] = idx++; } } graph; struct Query { int x[maxn], top[maxn], ans[maxn]; int nxt[maxn], head[maxn], idx; void Init(int n) { memset(head, -1, 4 * (n + 1)); idx = 0; } void Addquery(int tx, int tt) { if (tx == 1) ans[idx] = -1; x[idx] = tx; top[idx] = tt; nxt[idx] = head[tx]; head[tx] = idx++; } } query; struct Node { int p, v; }; multiset<int> mset; multiset<int>::iterator it; stack< pair<int, int> > stac; pair<int, int> par; void Init(int n) { graph.Init(n); query.Init(n); } void Solve() { mset.insert(-1); graph.sign[1] = 1; stac.push(make_pair(graph.head[1], -1)); while (!stac.empty()) { par = stac.top(); stac.pop(); int &p = par.first; if (p == -1) { mset.erase(mset.find(par.second)); } else { int &y = graph.pnt[p]; if (!graph.sign[y]) { graph.sign[y] = 1; int tp = p; p = graph.nxt[p]; stac.push(par); par.first = graph.head[y]; par.second = graph.val[tp]; stac.push(par); mset.insert(par.second); for (int i = query.head[y]; i != -1; i = query.nxt[i]) { it = mset.upper_bound(query.top[i]); it--; query.ans[i] = (*it); } } else { p = graph.nxt[p]; stac.push(par); } } } } int main() { int test, cas; scanf("%d", &test); for (cas = 1; cas <= test; cas++) { int n, m; int x, y, v, t; scanf("%d", &n); Init(n); for (int i = 1; i < n; i++) { scanf("%d %d %d", &x, &y, &v); graph.Addedge(x, y, v); } scanf("%d", &m); for (int i = 0; i < m; i++) { scanf("%d %d", &x, &t); query.Addquery(x, t); } Solve(); for (int i = 0; i < m; i++) { printf("%d/n", query.ans[i]); } } return 0; }