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Cod sursa(job #760401)
#include<cstdio>
#include<algorithm>
using namespace std;
#define maxn 100001
int n,t ;
int tata[maxn] ;
int nivel[maxn] ;
int x,y ;
int lca(int x,int y)
{
if( nivel[x] < nivel[y] )
swap ( x , y ) ;
int xnou = x ;
while( nivel[xnou] > nivel[y] )
xnou = tata[xnou] ;
int ynou = y ;
while( xnou != ynou )
{
xnou = tata[xnou] ;
ynou = tata[ynou] ;
}
return xnou ;
}
int main()
{
freopen("lca.in","r",stdin);
freopen("lca.out","w",stdout);
scanf("%d%d",&n,&t);
nivel[1] = 1 ;
for(int i=1;i<n;++i)
{
scanf("%d",&tata[i+1]);
nivel[i+1] = nivel[tata[i+1]] + 1 ;
}
++ t ;
while( -- t )
{
scanf("%d%d",&x,&y);
int sol = lca ( x , y ) ;
printf("%d\n",sol);
}
return 0;
}