CODEWITHSUNDEEP
carrays
Thu Ra
Thu Ra

Reputation: 2063

How to get count of elements in an array?

I created an array and put the value into array as follow

int *ptr_int;
int list_int[10];
int i;
for (i=0; i<10; i++)
    list_int[i] = i + 1;

and I assign a value into list_int array like this

list_int[17] = 18;

When I tried to get the count of array as follow

int size = sizeof(list_int ) / sizeof( int );
printf( "The size of int is %d.\n", size);

the result is only 10.

How could I get the array room count?

Upvotes: 0

Views: 135

Answers (4)

Mohamed Gaafar
Mohamed Gaafar

Reputation: 104

To Create Dynamic arrays ( allocated at run time ) 

int n; 

scanf("%d",&n); // read n from the user at run time 

int* x=(int*)malloc(sizeof(int)*n);  // where n is the number of elements you need to allocate

////// after that you can access the array (x) using indexer 

///// reading loop 
for(int i=0;i<n;i++)
scanf("%d",&x[i]);

===============================================================================

Note: if you need more dynamic data structure which can allocate memory for each entry you can use linked lists

Upvotes: 1

Yu Hao
Yu Hao

Reputation: 122373

list_int[17] = 18;

This is undefined behavior because the array size is only 10.

Note that with the exception of variable length arrays, sizeof operator is a compile time operator. The result of sizeof(list_int ) and sizeof(int) are determined in compile time.

To implement an array with dynamic size, you need to allocate the array dynamically, you may find realloc pretty helpful.

Upvotes: 1

MOHAMED
MOHAMED

Reputation: 43518

You have already defined the max size of your array as 10 with the following definition

int list_int[10];

You can not assign value to list_int[17]. Becacuse list_int[17] is out of the memory of the array list_int[10] that you have defined.

You can only assign value to the element from 0 .. 9

Upvotes: 1

cnicutar
cnicutar

Reputation: 182609

the result is only 10.

That's the real size. Assigning to list_int[17] is undefined behavior, and it does not magically extend the array.

Upvotes: 6

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