Cod sursă (job #238731)

#include <fstream>

using namespace std;

ifstream fin("pointeri.in");
ofstream fout ("pointeri.out");

#define MAX 200001

struct pointer
{
    int st, dr;
}a[MAX], fnl[MAX];

int n, rad, x[MAX], i;

void rez(int ind)
{
    if (a[ind].st == -1 && a[ind].dr == -1)
    {
        x[++i]=ind;
        return;
    }
    else if (a[ind].st == -1)
    {
        x[++i]=ind;
        rez(a[ind].dr);
    }
    else if (a[ind].dr == -1)
    {
        rez(a[ind].st);
        x[++i]=ind;
    }
    else
    {
        rez(a[ind].st);
        x[++i]=ind;
        rez(a[ind].dr);
    }
}
int main()
{
    //citire
    fin >> n >> rad;
    for (int j = 0; j<n; j++) fin >> a[j].st;
    for (int j = 0; j<n; j++) fin >> a[j].dr;

    rez(rad);

    fout << x[1] << '\n';

    x[0] = x[n+1] = -1;
    for (int j = 1; j<=n ; j++)
    {
        fnl[x[j]].st = x[j-1];
        fnl[x[j]].dr = x[j+1];
    }

    for (int j = 0; j<n ; j++) fout << fnl[j].st << ' ';
    fout << '\n';

    for (int j = 0; j<n; j++) fout << fnl[j].dr << ' ';
    fout << '\n';
    return 0;
}