思路：将边权排序，然后插入线段树，这样就可以直接用二分查找确定答案。
#pragma comment(linker, "/STACK:1024000000,1024000000") #include<set> #include<map> #include<cmath> #include<queue> #include<cstdio> #include<vector> #include<string> #include<cstdlib> #include<cstring> #include<iostream> #include<algorithm> #define pb push_back #define mp make_pair #define Maxn 100010 #define Maxm 200010 #define LL __int64 #define Abs(x) ((x)>0?(x):(-x)) #define lson(x) (x<<1) #define rson(x) (x<<1|1) #define inf 100000 #define lowbit(x) (x&(-x)) #define clr(x,y) memset(x,y,sizeof(x)) #define Mod 1000000007 using namespace std; int head[Maxn],vi[Maxn],dep[Maxn],w[Maxn],top[Maxn],son[Maxn],sz[Maxn],fa[Maxn],e,id; int val[Maxn]; int num[Maxn]; struct Point{ int val,i; int operator <(const Point &temp) const{ return val<temp.val; } }lis[Maxn]; struct Edge{ int u,v,next,val; }edge[Maxn*3]; struct Tree{ int l,r,c; int *p; int mid(){ return (l+r)>>1; } }tree[Maxn*3]; void init() { clr(head,-1);clr(vi,0); e=0;id=0; for(int i=0;i<Maxn*3;i++){ delete [] tree[i].p; } } void add(int u,int v,int val) { edge[e].u=u,edge[e].v=v,edge[e].val=val,edge[e].next=head[u],head[u]=e++; } void BuildTree(int l,int r,int po) { tree[po].l=l,tree[po].r=r,tree[po].c=0; tree[po].p=new int[r-l+2]; if(l==r) return ; int mid=tree[po].mid(); BuildTree(l,mid,lson(po)); BuildTree(mid+1,r,rson(po)); } void update(int i,int c,int po) { if(tree[po].l==tree[po].r){ tree[po].p[++tree[po].c]=c; return ; } tree[po].p[++tree[po].c]=c; int mid=tree[po].mid(); if(i<=mid) update(i,c,lson(po)); else update(i,c,rson(po)); } int getans(int l,int r,int val,int po) { if(l<=tree[po].l&&tree[po].r<=r){ int pos=lower_bound(tree[po].p+1,tree[po].p+tree[po].c+1,val)-tree[po].p; // cout<<tree[po].l<<" "<<tree[po].r<<" "<<l<<" "<<r if(pos>tree[po].c) return tree[po].p[tree[po].c]; if(tree[po].p[pos]==val) return val; if(pos>1){ return tree[po].p[pos-1]; } return -1; } int mid=tree[po].mid(); if(r<=mid) return getans(l,r,val,lson(po)); else if(l>=mid+1) return getans(l,r,val,rson(po)); else{ return max(getans(l,mid,val,lson(po)),getans(mid+1,r,val,rson(po))); } } void dfs(int u,int val) { vi[u]=1; int i,v; son[u]=0,sz[u]=1; num[u]=val; for(i=head[u];i!=-1;i=edge[i].next){ v=edge[i].v; if(vi[v]) continue; dep[v]=dep[u]+1; fa[v]=u; dfs(v,edge[i].val); if(sz[v]>sz[son[u]])son[u]=v; sz[u]+=sz[v]; } } void build(int u,int ti) { int i,v; w[u]=++id;top[u]=ti;vi[u]=1; lis[id].i=id,lis[id].val=num[u]; if(son[u]) build(son[u],ti); for(i=head[u];i!=-1;i=edge[i].next){ v=edge[i].v; if(vi[v]||v==son[u]) continue; build(v,v); } } void calc(int u,int c) { int f1=top[u]; int ans=-10000; while(f1!=1){ ans=max(ans,getans(w[f1],w[u],c,1)); u=fa[f1];f1=top[u]; } //cout<<w[f1]<<" "<<w[u]<<endl; ans=max(ans,getans(w[f1],w[u],c,1)); printf("%d ",ans); return ; } int main() { int t,n,i,j,u,v,val,q; scanf("%d",&t); while(t--){ init(); scanf("%d",&n); for(i=1;i<n;i++){ scanf("%d%d%d",&u,&v,&val); add(u,v,val); add(v,u,val); } dfs(1,1200000000); memset(vi,0,sizeof(vi)); build(1,1); sort(lis+1,lis+id+1); BuildTree(1,n,1); for(i=1;i<=n;i++){ update(lis[i].i,lis[i].val,1); } scanf("%d",&q); for(i=1;i<=q;i++){ scanf("%d%d",&u,&v); calc(u,v); } } return 0; }