sorting

#include <iostream>
#include <cmath>
using namespace std;
struct Elem{
    int * key;
    Elem* link;
    Elem(){
        key = NULL;
        link = NULL;
    }
};

int main(){
    //P = new Elem();
    int n;
    cout << "vvedite kol-vo zapisey" << endl;
    cin >> n;
    Elem *R;
    R = new Elem[n];
    cout << "vvedite kolithestvo cifr v kazdom chisle" << endl;
    int t;
    cin >> t;
    cout << "vvedite kluchi" << endl;
    int a[n];
    for (int i = 0; i < n; ++i){
        cin >> a[i];
        a[i] = a[i] % (unsigned int)pow(10,t);
        R[i].key = new int[t];
        for (int j = 0; j < t; ++j){
            R[i].key[j] = a[i] % 10;
            // cout << endl << R[i].key[j];
            a[i] /= 10;
        }
    }
    Elem Top[10];
    Elem Botm[10];
    Elem *P = &R[n-1];
    int p = n-1;
    for (int k = 0; k < t; ++k){
        for (int i = 0; i < 10; ++i){
            Top[i].link = &Botm[i];
            Botm[i].link = NULL;
        }
R3:
        int i = P->key[k];
        Top[i].link->link = P;
        Top[i].link = P;

        if(k==0 ){
            if(P!= NULL && p!=0){
                p--;
                P = &R[p];
                goto R3;
            }
        }else{
            P = P->link;
            if (P != NULL){
                goto R3;
            }
        }

        i = 0;
H2:
        P = &Top[i];
H3:
        i++;
        if(i==10){
            P->link = NULL;
            goto end;
        }
        if(Botm[i].link == NULL) goto H3;
        P->link->link = Botm[i].link;
        goto H2;
end:
        P = Botm[0].link;
    }

    cout << "Sorted:\n";
    while(P){
        for(int i = t-1;i>=0;i--) cout << P->key[i];
        cout << endl;
        P = P->link;
    }
    return 0;
}