Cod sursa(job #773782)

Utilizator veleanduAlex Velea veleandu Data 2 august 2012 16:20:20
Problema Stramosi Scor 90
Compilator cpp Status done
Runda Arhiva de probleme Marime 2.1 kb
// rezolvare off-line

#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

    typedef struct { long a,b,nro,rez; } query;
    query Q[300005];
    long i,n,m,x;
    long Nr[300005],nr,act;
    long Nr2[300005],nr2;
    long C[300005];
    vector <long> V[300005];

    void DFs ( long varf )
    {
        nr2=1;
        while ( nr2>0 )
        {
            //printf ("%d %d\n",varf,nr);
            if ( !C[varf] )
            {
                Nr[varf]=nr;
                nr++;
            }
            if ( C[varf] == (V[varf].size() ))
            // trecem inapoi
            {
                nr2--;
                varf=Nr2[nr2];
            }
            else{
                // mai bagam pe cineva in parcurgere

                nr2++;
                Nr2[nr2]=V[varf][C[varf]];
                C[varf]++;
                varf=Nr2[nr2];
            }
        }
    }
    bool mysort ( query a, query b )
    {
        return Nr[a.b]<Nr[b.b];
    }
    bool mysort2 ( query a, query b )
    {
        return a.nro<b.nro;
    }
    void DFs_2 ( long varf )
    {
        nr++;
        Nr[nr]=varf;
        long i;
        while ( Q[act].b == varf && varf!=0)
        {
            //printf ("%d %d %d %d\n", act, Q[act].a, Q[act].b, nr );
            if ( Q[act].a > nr )
                Q[act].rez=0;
            else
                Q[act].rez=Nr[nr-Q[act].a];
            act++;
        }
        for ( i=0; i<V[varf].size(); i++ )
        {
            DFs_2( V[varf][i] );
        }
        nr--;

    }

int main()
{
    freopen ("stramosi.in","r",stdin);
    freopen ("stramosi.out","w",stdout);
    scanf ("%d %d", &n, &m);
    for ( i=1; i<=n; i++ )
    {
        scanf ("%d", &x);
        V[x].push_back(i);
    }
    for ( i=1; i<=m; i++ )
    {
        scanf ("%d %d", &Q[i].b, &Q[i].a);
        Q[i].nro=i;
    }
    DFs(0);
    sort ( Q+1, Q+m+1, mysort );
    nr=0;
    act=1;
    Nr[0]=0;
    DFs_2(0);
    sort ( Q+1, Q+m+1, mysort2 );

    for ( i=1; i<=m; i++ )
        printf ("%d\n",Q[i].rez);
}