#include <cstdio>
#include <cstdlib>
#include <vector>
using namespace std;
#define MAXN 10010
vector<int> Tree[MAXN], query[MAXN];
int Set[MAXN], num[MAXN],root[MAXN], ancestor[MAXN];
bool visite[MAXN];
int n;
void initial()
{
for( int i= 0; i<= n; ++i )
Tree[i].clear(), num[i]= 1, query[i].clear();
memset( root, false, sizeof(root) );
memset( visite, false, sizeof(root) );
memset( ancestor, 0, sizeof(ancestor) );
}
void make_set( int u )
{
Set[u]= u;
}
int find( int u )
{
while( u!= Set[u] ) u= Set[u];
return u;
}
void union_set( int u, int v )
{
int a= find(u), b= find(v);
if( num[a]> num[b] ) Set[b]= a;
else
{
Set[a]= b;
if( num[a]== num[b] ) num[b]++;
}
}
void l_c_a( int u )
{
make_set( u );
ancestor[u]= u;
for( size_t i= 0; i< Tree[u].size(); ++i )
{
l_c_a( Tree[u][i] );
union_set( u, Tree[u][i] );
ancestor[ find(u) ]= u;
}
visite[u]= true;
for( size_t i= 0; i< query[u].size(); ++i )
if( visite[ query[u][i] ] )
{
printf("%d\n", ancestor[ find( query[u][i] ) ] );
return;
}
}
int main()
{
int test;
scanf("%d",&test);
while( test-- )
{
int a, b;
scanf("%d",&n);
initial();
for( int i= 0; i< n- 1; ++i )
{
scanf("%d%d",&a,&b);
Tree[a].push_back(b);
root[b]= true;
}
scanf("%d%d",&a,&b);
if( a== b ) query[a].push_back(a);
else
{
query[a].push_back(b);
query[b].push_back(a);
}
for( int i= 1; i<= n; ++i )
if( !root[i] )
{
l_c_a(i);
break;
}
}
return 0;
}
posted on 2009-02-27 14:00
Darren 閱讀(313)
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