Thread: dynamic array and structure problem

  1. #1
    Registered User bluetxxth's Avatar
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    dynamic array and structure problem

    Hi all,

    I have been trying to make a program to test pointers and structures amongst other things. I have tried to reduce it to the minimal expression because this is where the problem is. The code consists on a structure, three functions (one of which is just a menu).

    The two important functions are

    employee create();
    print_employee();

    The objective now is to create an dynamic array of employees and then output the information for a particular employee which I choose by pointing to it with a pointer.

    All works fine including memory allocation except that when I, for example, choose to enter two employee records and then later I want to output employee id number one, I still get the output for the last employee entered, that is, the output for employee number two. I think there is something wrong either with the variables I call or with the pointers.

    Can anybody hep? code below...

    Thank you,

    bluetxxth


    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    //Structure - can I not bury this inside the a function? how to access it later...?
    typedef struct employee {
        int emp_index; //To assign a value to each employee for a later "pointing"
        char name[30];
        char address[100];
        int age;
        float salary;
    }employee;
    
    
    // Takes imput that establishes the size of the staff
    
    
    int staff_size(int emp_num) {
    
        printf("What is the size of your staff?: ");
        scanf("%d", &emp_num);
    
        return emp_num;
    }
    
    //Takes empoyee data input from user
     employee_create(int emp_num, employee *emp_rec, employee **emp_id) {
    
        
        printf("\nEnter employee id: ");
        scanf("%d", &emp_rec[emp_num].emp_index);
        printf("\nEnter the name of the employee: ");
        scanf("%s",emp_rec[emp_num].name);
        printf("\nEnter the address of the employee: ");
        scanf("%s", emp_rec[emp_num].address);
        printf("\nEnter the age of the employee: ");
        scanf("%d", &emp_rec[emp_num].age);
        printf("\nEnter the salary of the employee: ");
        scanf("%f", &emp_rec[emp_num].salary);
    
        //this is an array of id which takes emp_index as the index which in turn is a pointer which has a pointer with an index as its index and which accesses the emp_index value
        emp_id[emp_rec[emp_num].emp_index] = &emp_rec[emp_num];
        
    }
    
    
    void print_employee(employee **emp_id , int emp_num) {
        printf("Enter employee you want to inspect: ");
        scanf("%d",&emp_num);
        printf("\nEmployee summary: Id: %d \nName: %s \nAddress: %s \nAge: %d \nSalary: %f", emp_id[emp_num]-> emp_index, emp_id[emp_num]->name, emp_id[emp_num]->address, emp_id[emp_num]->age, emp_id[emp_num]->salary);//Prints desired employee
    
    }
    
    
    void menu() {
    
        printf("----------------------------------------\n");
        printf("|Choose amongst the following options: |\n");
        printf("----------------------------------------\n");
        printf("| 1- Enter employee data:              |\n");
        printf("| 2- inspect employees:                |\n");
        printf("----------------------------------------\n\n");
    }
    
    int main(void) {
    
        int d = 0,  emp_num =0, k;
        int option;
        employee *emp_rec;
        employee **emp_id;
        
    
       employee emp_struct; // Structure declaration
    
    
       emp_rec = malloc (sizeof(emp_struct)*emp_num); // dynamic memory allocation for an array of records
       emp_id = malloc (sizeof(emp_struct)*emp_num);// dynamic memory allocation for an array of employee ids
    
    
    //generate menu
       menu();
    
        while (option != 0) {
    
            switch (option) {
    
                case 1: printf("\nEnter employee data: ");
                         for(d = 0; d < staff_size(emp_num) ; d++){
                          employee_create(emp_num, emp_rec, emp_id);
                          break;
                            }break;
    
                
                case 2: printf("\nInspect employee: ");
                        print_employee(emp_id, k);
                        break;
                        
    
            }
    
            printf("\nSelect an option: ");
            scanf("%d", &option); //Returns to default state
    
            //exit while loop
        }
    
       free(emp_rec);
       free(emp_id);
    
        return (0);
    }

  2. #2
    Registered User
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    For the simple reason that array indexes start at 0 not 1.
    So employee number 1 would be emp_id[emp_num-1].

  3. #3
    Hurry Slowly vart's Avatar
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    since your emp_num is 0 you are allocating 0 bytes for your arrays. how you plan to store anything there?
    All problems in computer science can be solved by another level of indirection,
    except for the problem of too many layers of indirection.
    David J. Wheeler

  4. #4
    Registered User bluetxxth's Avatar
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    Excuse my delay,

    Thank you for the answer. I will test it and get back to this.

    br,

    bluexxth

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