1 #include<cstdio> 2 #include<cstdlib> 3 #include<cstring> 4 #include<cmath> 5 #include<algorithm> 6 #include<queue> 7 #include<stack> 8 #include<deque> 9 #include<map> 10 #include<iostream> 11 using namespace std; 12 typedef long long LL; 13 const double pi=acos(-1.0); 14 const double e=exp(1); 15 const int N = 10100; 16 17 #define lson i << 1,l,m 18 #define rson i << 1 | 1,m + 1,r 19 int cnt,ans; 20 int a,b,n; 21 int root; 22 int head[N]; 23 int is_root[N]; 24 int father[N]; 25 int vis[N]; 26 27 struct edge 28 { 29 int to; 30 int next; 31 } edge[N]; 32 33 int seek(int ss) 34 { 35 int mid; 36 int head=ss; 37 while(ss!=father[ss]) 38 ss=father[ss]; 39 40 while(head!=ss) 41 { 42 mid=father[head]; 43 father[head]=ss; 44 head=mid; 45 } 46 return ss; 47 } 48 49 void join(int xx,int yy) 50 { 51 int one=seek(xx); 52 int two=seek(yy); 53 if(one!=two) 54 father[two]=one; 55 } 56 57 void add(int x,int y) 58 { 59 edge[cnt].to=y; 60 edge[cnt].next=head[x]; 61 head[x]=cnt++; 62 } 63 64 void init() 65 { 66 int i,p,j; 67 int x,y; 68 cnt=0; 69 memset(head,-1,sizeof(head)); 70 memset(is_root,0,sizeof(is_root)); 71 memset(vis,0,sizeof(vis)); 72 scanf("%d",&n); 73 for(i=0; i<=n; i++) 74 father[i]=i; 75 for(i=1; i<n; i++) 76 { 77 scanf("%d%d",&x,&y); 78 add(x,y); 79 is_root[y]=1; 80 } 81 for(i=1; i<=n; i++) 82 if(is_root[i]==0) 83 root=i; 84 } 85 86 void LCA(int u) 87 { 88 int i,p,j; 89 for(i=head[u]; i!=-1; i=edge[i].next) 90 { 91 int v=edge[i].to; 92 LCA(v); 93 join(u,v); 94 vis[v]=1; 95 } 96 97 if(u==a&&vis[b]==1) 98 ans=seek(b); 99 if(u==b&&vis[a]==1) 100 ans=seek(a); 101 102 return ; 103 } 104 105 void solve() 106 { 107 scanf("%d%d",&a,&b); 108 // vis[root]=1; 109 LCA(root); 110 } 111 112 int main() 113 { 114 int t,m,i,p,j; 115 scanf("%d",&t); 116 for(i=1; i<=t; i++) 117 { 118 init(); 119 solve(); 120 121 printf("%d ",ans); 122 } 123 return 0; 124 }