How to delete an array of struct without affecting the others element index in C?

Question

I have a problem. I have an array of struct. In my program, I have two options or menu, which are add and delete. But, when I delete one element from the array, it will affect the other element's index. So, when I delete an element and do some addition, it will causes an error. How can I solve it?

Here is my code :

#include "stdio.h"
#include "string.h"

struct itemlist
{
    char name[25];
    int quantity;
};

int main()
{
    int progress,processNum,i,sizeStruct = 0;
    struct itemlist items[105];
    printf("How many progress you want to do?\n");
    scanf("%d",&progress); getchar();

    for(i = 0; i < progress ; i++){
        scanf("%d",&processNum); getchar();        
        switch (processNum){
        case 1: // Add
            printf("Name of item :\n");
            scanf("%[^\n]",items[i].name); getchar();
            printf("How many items?:\n");
            scanf("%d",&items[i].quantity); getchar();
            sizeStruct++;
            printf("Success to add!!\n"); 
            break;
        case 2: // Delete from database, and its last index can be replaced.
            int index3;
            printf("Which index do you wanna delete?\n");
            scanf("%d",&index3); getchar();
            for(int k = index3-1; k < sizeStruct - 1; k++){
                items[k] = items[k + 1];
            }
            sizeStruct--;
            printf("Your item has been deleted.\n"); 
            break;
        }
    }
    // Scan All last Items
    for(int j = 0; j < sizeStruct; j++){
        printf("%s\n",items[j].name);
    }

    return 0;
}

This is the example of deleting the last index without addition, which is works :

How many progress you want to do?
3
1
Name of item :
Cola-Cola
How many items?:
3
Success to add!!
1
Name of item :
Sprite
How many items?:
1
Success to add!!
2
Which index do you wanna delete?
1
Your item has been deleted.
Sprite // List of items

Here is my code when i'm trying to add some element after I did some deletion.

How many progress you want to do?
4
1
Name of item :
Cola-Cola
How many items?:
3
Success to add!!
1
Name of item :
Sprite
How many items?:
4
Success to add!!
2
Which index do you wanna delete?
2
Your item has been deleted.
1
Name of item :
Beer
How many items?:
8
Success to add!!
Cola-Cola
Sprite // Supposed to be Beer, because Sprited already deleted.

Himanshu Singh · Accepted Answer · 2019-12-03 05:56:35Z

2

There are two possible approaches:-

Use some other data structure like linked list because the way you want thing can't be done using array.
If you have to use array, then mark the element at index 'i' which you want to delete with some unique value like items[i].quantity = INT_MIN or items[i].quantity = -1. Through this you'll be easily able to identify which element has been deleted by checking array elements which have quantity as a negative value.

answered Dec 3, 2019 at 5:56

Himanshu Singh

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3 Comments

Bone Shaw Over a year ago

If I use method 2, can that index be replaced with another elements?

Himanshu Singh Over a year ago

if you meant that overwriting can be done at that index with some other values. Then yes.

Bone Shaw Over a year ago

Can I just remove it with malloc or memset?

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