Parcurgere arbori RSD SRD SDR

#include<iostream>
#include<fstream>
using namespace std;
ifstream f("arbore.in");
int S[20], D[20], n, r;
void RSD(int nod)
{
    if(nod)
    {
        cout<<nod<<" ";
        RSD(S[nod]);
        RSD(D[nod]);
    }
}
void SRD(int nod)
{
    if(nod)
    {
        SRD(S[nod]);
        cout<<nod<<" ";
        SRD(D[nod]);
    }
}
void SDR(int nod)
{
    if(nod)
    {
        SDR(S[nod]);
        SDR(D[nod]);
        cout<<nod<<" ";
    }
}
int main()
{
    int i,j, OK;
    f>>n;
    for(i=1; i<=n; ++i)
        f>>S[i];
    for(j=1; j<=n; ++j)
        f>>D[j];
    ///caut radacina
    for(i=1; i<=n; i++)
    {
        OK=0;
        ///presupun ca i 'apartine taiat' S[], i 'apartine taiat' D[] <=> i este radacina
        for(j=1; j<=n; j++)
            if(S[j]==i||D[j]==i)
                OK=1;
        if(!OK)
            r=i;
    }
    cout<<"RSD:";
    RSD(r);
    cout<<"\nSRD:";
    SRD(r);
    cout<<"\nSDR:";
    SDR(r);
}
/*
abore.in
7
0 3 5 1 0 0 0
0 4 7 0 0 0 6
*/