How to insert multiple elements in array in c program? - c

Question

I can insert an element in an array but I want to know that is this possible to insert multiple(two or three..) element in an array by using c program. I tried a little, there is no problem or eror but it doesn't work.
Here is my code which I had tried to make a program which can insert multiple element in array:
#include<stdio.h>
int main(){
int size,i;
printf("Enter array length - ");
scanf("%d",&size);
int array[size];
printf("Enter array elements : \n");
for(i=0; i<size; i++){
scanf("%d",&array[i]);
}
int el_no; //el_no means elemnet no which user should input
printf("How many element you want to insert - ");
scanf("%d",&el_no);
int element[el_no];
printf("Element value - ");
for(i=0; i<el_no;i++){
scanf("%d",&element[i]);
}
int index[el_no];
printf("Index no - ");
for(i=0; i<el_no;i++){
scanf("%d",&index);
}
for(i=0; i<el_no;i++){
for(i=index[i]; i< size+el_no;i++){
array[i+1]=array[i];
}
}
for(i=0; i<el_no; i++){
array[index[i]]=element[i];
}
for(i=0; i<size+el_no; i++){
printf("%d\t",array[i]);
}
return 0;
}

Answer 1

You can't do what you want (at least, not directly). Once you say
int array[size];
that array can only hold size number of elements, no more.
Your program first stores values into array[0], array[1], ..., up to array[size-1]. That's perfectly fine.
But then when you say
for(i=0; i<el_no;i++){
for(i=index[i]; i< size+el_no;i++){
array[i+1]=array[i];
}
}
you are trying to move some of the array's elements over (to make room for new ones), but you're moving them outside the array, which is never going to work.
One fix (not quite what you want) would be to declare the array bigger than it needs to be. For example, you could say
int array[size+5];
and then later double-check that it will be big enough:
printf("How many element you want to insert - ");
scanf("%d",&el_no);
if(el_no > 5) {
printf("sorry, I can't insert that many\n");
exit(1);
}
The "better" way, although it gets into pointers and dynamic memory allocation perhaps sooner than you're ready to, would be to use a pointer simulating an array, using malloc to allocate space for it to point to:
int *array = malloc(size * sizeof(int));
Than, later, you can resize it:
array = realloc(array, (size + el_no) * sizeof(int));
This is just an example -- in reality, you'd need to check the return values of malloc and realloc to make sure they're not NULL, indicating that something has gone wrong.
Also there are some other problems with your code. The way you're using the auxiliary index array looks wrong, and probably isn't necessary at all.

Answer 2

As I tried to show in my comment, you're not specifying an index for the index array. In that loop, you're scanfing to &index, which is the wrong argument for scanf. Your compiler should be giving you a warning:
warning: format '%d' expects argument of type 'int *', but argument 2 has type 'int (*)[el_no]' [-Wformat=]
32 | scanf("%d",&index);
| ~^ ~~~~~~
| | |
| | int (*)[el_no]
| int *
Despite the warning, what's most likely happening is each value you enter in the loop is getting stored at index[0]. You need to change that loop from
for(i=0; i<el_no;i++){
scanf("%d",&index);
}
to
for(i=0; i<el_no;i++){
scanf("%d",&index[i]); // <-- note the [i] addition
}
You've done this correctly in the previous loop
for(i=0; i<size; i++){
scanf("%d",&array[i]);
}
This may not be the only problem, but it's a problem, and too long for a comment.

Answer 3

I've edited the code and stated where to correct the faults
#include<stdio.h>
int main(){
Initialize j here
int size,i,j;
printf("Enter array length - ");
scanf("%d",&size);
int array[size];
printf("Enter array elements : \n");
for(i=0; i<size; i++){
scanf("%d",&array[i]);
}
int el_no; //el_no means elemnet no which user should input
printf("How many element you want to insert - ");
scanf("%d",&el_no);
int element[el_no];
printf("Element value - ");
for(i=0; i<el_no;i++){
scanf("%d",&element[i]);
}
int index[el_no];
printf("Index no - ");
here is a mistake you can correct
for(i=0; i<el_no;i++){
scanf("%d",&index[i]);//Add[i] here
}
Also do not use same variable in more than one for loop in a nested loop
for(i=0; i<el_no;i++){
for(j=index[i]; j< size+el_no;j++){//Use any other variable than 'i' in this for loop
depending on what you want to do you can correct this line below
array[i+1]=array[i];
}
}
for(i=0; i<el_no; i++){
array[index[i]]=element[i];
}
for(i=0; i<size+el_no; i++){
printf("%d\t",array[i]);
}
return 0;
}
All is good.
Hope you find it useful.