jzoi#13t1

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<algorithm>
 4 #include<cmath>
 5 #include<cstring>
 6 #include<cstdlib>
 7 #include<ctime>
 8 #include<vector>
 9 #define intree(u,v) (id[u]<=R[v]&&id[u]>=L[v])
10 #define Rep(i,k) for(int i=first[k];i;i=next[i])
11 #define lowbit(a) ((a)&(-(a)))
12 #define clr(a,x) memset(a,x,sizeof(a))
13 #define rep(i,l,r) for(int i=l;i<(r);i++)
14 typedef long long ll;
15 using namespace std;
16 int read()
17 {
18     char c=getchar();
19     int ans=0,f=1;
20     while(!isdigit(c)){
21         if(c==‘-‘) f=-1;
22         c=getchar();
23     }
24     while(isdigit(c)){
25         ans=ans*10+c-‘0‘;
26         c=getchar();
27     }
28     return ans*f;
29 }
30 struct edge{
31     int u,v;
32 };
33 const int maxn=2000009;
34 int n,m,dfstime=0,cnt=0,next[maxn],c[maxn],first[maxn],id[maxn],L[maxn],R[maxn],dep[maxn];
35 edge E[maxn];
36 int e[maxn<<1];
37 void dfs(int k,int f){
38     L[k]=id[k]=++dfstime;
39     Rep(i,k){
40         if(e[i]!=f){
41             dep[e[i]]=dep[k]+1;
42             dfs(e[i],k);
43         }
44     }
45     R[k]=dfstime;
46 }
47 int main()
48 {    
49     freopen("tree.in","r",stdin);
50     freopen("tree.out","w",stdout);
51     n=read();
52     rep(i,1,n){
53         int from=read(),to=read();
54         e[++cnt]=to;
55         if(!first[from]) first[from]=cnt;
56         next[c[from]]=cnt;
57         c[from]=cnt;
58         e[++cnt]=from;
59         if(!first[to]) first[to]=cnt;
60         next[c[to]]=cnt;
61         c[to]=cnt;
62         E[i].u=from;E[i].v=to;
63     }
64     dfs(1,0);
65     m=read();
66     while(m--){
67         int from=read(),to=read(),t=read();
68         int u=E[t].u,v=E[t].v;
69         if(dep[u]>dep[v]) swap(u,v);
70         if((intree(from,v)&&!intree(to,v))||(!intree(from,v)&&intree(to,v)))
71         puts("NO");
72         else puts("YES");
73     }
74     fclose(stdin);
75     fclose(stdout);
76     return 0;
77 }