Pagini recente » Cod sursa (job #1952270) | Cod sursa (job #2097560) | Cod sursa (job #28151) | Cod sursa (job #1743570) | Cod sursa (job #1690825)
#include <cstdio>
using namespace std;
int n,tata[100001],a[20][100001],niv[100001],m,p;
void dfs(int x,int lev)
{
if(tata[x]){if(niv[tata[x]]){niv[x]=niv[tata[x]]+lev;return;}dfs(tata[x],lev+1);}
}
int query(int r,int q, int p)
{
int i,j,c;
if(niv[r]<niv[q]){c=r;r=q;q=c;}
for(j=p;j>=0;j--)
if(a[j][r]&&niv[a[j][r]]>=niv[q])
{r=a[j][r];if(niv[r]==niv[q])break;}
else if(niv[r]==niv[q])break;
for(j=p;j>=0;j--)
{
if(a[j][r]&&a[j][r]!=a[j][q]){r=a[j][r];q=a[j][q];}
}
if(r==q)return r;
return tata[r];
}
int main()
{
int i,j,k,p,r;
freopen("lca.in","r",stdin);
freopen("lca.out","w",stdout);
scanf("%d%d",&n,&m);
for(i=2; i<=n; i++)
{
scanf("%d",&p );
tata[i]=a[0][i]=p;
}
tata[1]=a[0][1]=0;
niv[1]=1;
for(i=2;i<=n;i++)
dfs(i,1);
k=n;p=-1;
while(k){p++;k/=2;}
for(j=1;j<=p;j++)
for(i=1;i<=n;i++)
if(a[j-1][i])a[j][i]=a[j-1][a[j-1][i]];
for(i=0;i<m;i++)
{
scanf("%d%d",&r,&k);
int rasp=query(r,k,p);
printf("%d\n",rasp);
}
return 0;
}