kak zhe ya ebal infu

#include <iostream>
#include <stdlib.h>
#include <string.h>
#include <fstream>
#include <stdio.h>
using namespace std;

typedef struct stud{
   char *first_name, *last_name;
   int year, month, day;
   double av_grade;
   struct stud *next;
};

void push(stud **head, char *first_name, char *last_name, int year, int month, int day, double av_grade) {
    stud *tmp = (stud*) malloc(sizeof(stud));
    tmp->first_name = (char*) malloc(strlen(first_name));
    strcpy(tmp->first_name, first_name);
    tmp->last_name = (char*) malloc(strlen(last_name));
    strcpy(tmp->last_name, last_name);
    tmp->year = year;
    tmp->month = month;
    tmp->day = day;
    tmp->av_grade = av_grade;
    tmp->next = *head;
    *head = tmp;
}
void pop(stud **head) {
    stud* prev = NULL;
    if (head == NULL){
        cout << "Node Error" << endl;
        exit(1);
    }
    prev = *head;
    *head = (*head)->next;
    free(prev);
}
void write_to_file(stud *head, FILE *target) {
    int flag = 0;
    while (head != NULL) {
        if (flag == 0) {
            fprintf(target, "%s", head->first_name);
            flag = 1;
        }
        else
            fprintf(target, "\n%s", head->first_name);
        fprintf(target, "%s", head->last_name);
        fprintf(target, "%d\n", head->day);
        fprintf(target, "%d\n", head->month);
        fprintf(target, "%d\n", head->year);
        fprintf(target, "%f", head->av_grade);
        head = head->next;
    }
}
void pr_b(stud *head) {
    while (head) {
        cout <<  head->first_name << " " << head->last_name << endl;
        cout << "Date of Birth: " << head->day << "." << head->month << "." << head->year << endl; ;
        cout << "Av_grade: " <<  head->av_grade << endl << endl;
        head = head->next;
    }
    cout << endl;
}
stud* getNth(stud* head, int n) {
    int c = 0;
    while (c < n && head) {
        head = head->next;
        c++;
    }
    return head;
}

void deleteNth(stud **head, int n) {
    if (n == 0)
        return pop(head);
    else {
        stud *prev = getNth(*head, n - 1);
        stud *elm = prev->next;
        prev->next = elm->next;
        free(elm);
    }
}

int main(){
    stud *head = NULL;
    char  first_name[50], last_name[50], name_file[100], buf[10];
    int year, month, day;
    double av_grade;
    int act;
    FILE* source;
    char k[10];
   cout << "Enter way" << endl;
   int n = 0;
   while(n != 3){
    cin >> act;
     switch (act) {

            case 1: {
                cout << "Enter file name:";                    //Чтение из файла
                cin >>  name_file;
                if ((source = fopen(name_file, "rw")) == NULL)
                   cout << "File error!" << endl;

                while (fgets(first_name, 64, source) != NULL) {
                    fgets(last_name, 32, source);
                    fgets(buf, 10, source);
                    year = atoi(buf);
                    fgets(buf, 10, source);
                    month = atoi(buf);
                    fgets(buf, 10, source);
                    day = atoi(buf);
                    fgets(buf, 10, source);
                    av_grade = atof(buf);

                    push(&head, first_name, last_name, year, month, day, av_grade);

                }
                fclose(source);
                break;
            }
            case 2: {
                 printf("New file name:\n");
                scanf("%s", name_file);
                FILE *target;
                target = fopen(name_file, "w");
                write_to_file(head, target);
                fclose(target);
                cout << "done" << endl;
                break;
            }

            case 3:{
                pr_b(head);
                break;
            }
            case 4: {
                cout << "Surname, first name" << endl;
                cin >> last_name >> first_name;
                cout << "Enter date of birth (DD MM YYYY):" << endl;
                cin >> day >> month >> year;
                cout << "Grade point average:" << endl;
                cin >> av_grade;
                push(&head, first_name, last_name, year, month, day, av_grade);
                break;
            }
            case 5: {
                cout << "Base Plot File:" << endl;
                cin >> name_file;
                source = fopen(name_file, "r");

                while (fgets(first_name, 64, source) != NULL) {
                    fgets(last_name, 64, source);
                    fgets(buf, 10, source);
                    year = atoi(buf);
                    fgets(buf, 10, source);
                    month = atoi(buf);
                    fgets(buf, 10, source);
                    day = atoi(buf);
                    fgets(buf, 10, source);
                    av_grade = atof(buf);

                    push(&head, first_name, last_name, year, month, day, av_grade);
                }
                break;
            }

            case 6: {
                int n = 0;
                stud* prev = head;
                cout << "Enter last name:" << endl;
                cin >> last_name;
                sprintf(last_name, "%s%s", last_name, "\n\0");
                while (prev != NULL) {
                    if (!strcmp(last_name, prev->last_name)) {
                        deleteNth(&head, n);
                        cout << "done" << endl;
                    }
                prev = prev->next;
                n++;
                }

                break;
            }
            case 7: {
                cout << "First name:" << endl;
                cin >> first_name;
                cout << "Surname" << endl;
                cin >> last_name;
                sprintf(first_name, "%s%s", first_name, "\n\0");
                sprintf(last_name, "%s%s", last_name, "\n\0");
                stud* prev = head;
                while (prev != NULL) {
                if (!strcmp(first_name, prev->first_name) && !strcmp(last_name, prev->last_name)) {
                    cout << "Last name:" <<  prev->first_name << endl;
                    cout << "First name: %s" << prev->last_name << endl;
                    cout << "Date of Birth:" <<  prev->day << prev->month << prev->year;
                    cout << "Av_grade: %\n\n"<< prev->av_grade << endl;

                prev = prev->next;
                }
                break;
            }

        }
         case 8: {
            n = 3;
            return n;
         }
    }
   }
}