initialising every elements of an array to 0 in c

general
,
1

At the time of declaration i can initialize every elements of an array to ‘0’ in C using calloc() or statements like :

int a[10]={0};

but I want to reset all the elements to ‘0’ after every iteration of a loop.
Can it be done without declaring the array again? (In the example statement above I am declaring the array too)

I am just looking for the fastest possible way of initializing all the elements of an array to zero.

2

simply use for loop or memset, there is no magic construction to achieve the same…

2 Likes
3

obviously loop can be used but i needed something which would consume lesser time. memset seems good. thanks :slight_smile:

4

What did you mean by “without declaring the array again”? If that didn’t mean declaring the array inside the loop, then you can try that as well.

Something like this:

int main()
{
    ...
    while (t--)
    {
        int arr[] = {0};
        ...
    }
    ...
}

And do forget about this, if this is what you meant!! :slight_smile:

2 Likes
5

If you are facing TLE problem, then memset won’t help probably…

6

By “without declaring the array again”, I mean that using “int a[10]={0}” will initialize all elements to zero but it will also re-declare the array. I don’t need to declare the array again. I am just looking for the fastest possible way of initializing all the elements of an array to zero.

7

I am not facing TLE problem. I am just looking for the fastest possible way of initializing all the elements of an array to zero.

8

int a[n]={0}; also take O(n) time to initilise…it doesnt affect running time to much whether ur initilising by foor-loop,or memset or int a[n]={0}; although there are some crazy techniques which can initilise an array in O(1) time. but not worth implementing in contests.

2 Likes
9

memset() gives TLE sometimes on codechef

10

what do u mean is there anything wrong with codechef or memset

11

@princerk, i think there is sth wrong with codechef. last month’s long challenge easiest question gave TLE, just becuase of memset(). thank God, sb discussed it on forum and then i realized the reason of TLE and changed it with for loop and got AC, though memset() was faster. admins here horrible, i am pretty sure that they havent fixed that bug yet. for comparison: http://stackoverflow.com/questions/7367677/is-memset-more-efficient-than-for-loop-in-c.