CODEWITHSUNDEEP
carrays
Aditya Vikas Devarapalli
Aditya Vikas Devarapalli

Reputation: 3473

Initializing all elements of an array to 0's

In C Language i'm creating a array ( 2 Dimensional ) in which all the elements are zeros

I do it the following way :

int a[5][5],i,j;  //a is the required array
for(i=0;i<5;i++)
   for(j=0;j<5;j++)
       a[i][j]=0;

I know some other way also :

int a[5][5]={0};

Are both the same or is there any difference ??

What should be preferred ??

Thank you !

Upvotes: 3

Views: 1297

Answers (4)

haccks
haccks

Reputation: 106002

I would prefer latter one if I do not want to over stress my eyes (and my compiler too).

Upvotes: 0

user1814023
user1814023

Reputation:

Second one is useful. The first one uses for loop, so it takes time. There are other ways in which you can initialize an arrray...

int myArray[10] = { 5, 5, 5, 5, 5, 5, 5, 5, 5, 5 }; // All elements of myArray are 5
int myArray[10] = { 0 };    // Will initialize all elements to 0
int myArray[10] = { 5 };    // Will initialize myArray[0] to 5 and other elements to 0
static int myArray[10]; // Will initialize all elements to 0
/************************************************************************************/
int myArray[10];// This will declare and define (allocate memory) but won’t initialize
int i;  // Loop variable
for (i = 0; i < 10; ++i) // Using for loop we are initializing
{
    myArray[i] = 5;
}
/************************************************************************************/
int myArray[10] = {[0 ... 9] = 5}; // This works in GCC
memset(myArray, 0, sizeof(myArray));

Upvotes: 3

Sergey L.
Sergey L.

Reputation: 22542

Both ways have the same effect, but the second one will generally be faster because it allows the compiler to optimise and vectorise that code.

Another widely accepted way (also optimisable) is

memset(a, 0, sizeof(a));

Upvotes: 6

Fiddling Bits
Fiddling Bits

Reputation: 8861

The second method is more concise. Also consider:

memset(&a, 0, sizeof(a));

Upvotes: 6

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