C Language: How to initialize an integer array with 0?

Hello, Guys,

To initialize an integer array I usually use a for loop, something like:

for(i=0: i<n; i++)

Like I did in this solution:

I’m wondering if there is an easier and faster way to do it. I checked online that it is possible to do “array[10]={0}” or “array[10]={ }”, but I tested on codechef compiler for C and it does not work.

Do you know of any other way to do it that works on codechef compiler for C?

Thanks in advance for the help. :slight_smile:

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int arr[10]={0};
its working fine. check it

Initialising an array can be done in the following way:

int a[100];
// a[0] will be some garbage value, but rest all will be 0's.

Initialising with 0

// Static way of initialisation
int a[100] = {0}; // all elements will be 0

// Or use #define to define the size of array.
#define size 10000
int b[size] = {0}; // All elements will be 0 in this case too

// The following doesn't work
int n = 100;
int c[n] = {0};  // error: variable-sized object may not be initialized
Initialising with some other value (say 15)

// The following doesn't work
int a[100] = {15}; // a[0] will be 15, but rest all values will be 0

// Use for loop to initialise
int a[100];
for(int i=0;i<100;i++)
    a[i] = 15;

// Initialisation won't affect the time complexity, since O(n) loops are lightning fast in C.
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I’ll just add this here, but you could use a vector, which initializes all elements to 0 by default.

vector<int> v(size);

memset(array, 0, sizeof(array));

here all the elements of the array will be initialized to 0
you can also set the number of bytes you want to initialize (from the starting of the array)
something like this

memset(array, 0, n * sizeof(arr[0]));

will initialize first n elements to 0

note-> you have to add the header <memory.h> or <string.h> in order to use memset function!

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Thank you suman_18733097, I tested each example and worked exactly as you mentioned. Thanks for your contribution. I think I was having problem with variable sized array.

You are correct, sourav2901. I tested and It works for a fixed sized array.

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Thanks, inclusiveor. I tried this :

But I get this error:

I tried some google about this type, but did not find anything about that.

Thanks for the help anyways. :grinning:

Thank you for the help, eraldo_coil. It also works for variable sized arrays. That is cool. Thanks for your contribution.

I noticed that it does not work with values different than zero in the second argument of the function right? It seems to work with strings, but not with int arrays. I am trying for example:
memset(array, 10, n * sizeof(arr[0]));

Yeah, memset cannot be used to fill an Integer array with values other than {-1,0}.
You can refer about it here.

Oh sorry, I misunderstood this discussion to be about C++. My bad.

For using vectors, include the “vector” header file:


or if you wanna be lazy about including the required header files for the particular problem statement, you can include this one header file:


This header file contains all the necessary header files such as iostream, algorithm, vector, math, and many useful functions!

What I stated above regarding vectors and that other header file "bits/stdc++.h> is possible in C++.

In C though, you’ll have to use arrays!

int a[size] = {0};

works just fine, where “size” is the size of the array. I checked it in codechef C compiler.

Well, as stated earlier in this discussion,

when we try to initialise entire array elements with non-zero element in this manner, only first element will take the value. Rest all will be 0.

You should have even tested for non-zero values.

bro can you do this

@suman_18733097 ok alright! I didn’t test for non zero values, since the question up above was requiring the answer for only zero. My bad!