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c++arraysinitializationcurly-braces
Mr.Trent
Mr.Trent

Reputation: 15

Brace initialization in arrays c++

I want to know how to intialize values to some elements of array such as. 

int arr[5]={3,5,6};

in a way that the index of 3 is 0 and 5 is 2.
So index 1 is skipped and automatically assigned value by compiler!

Thanks for the help!

Upvotes: 1

Views: 4073

Answers (2)

eerorika
eerorika

Reputation: 238311

I want to know how to intialize values to some elements of array ... So index 1 is skipped

This is not possible. It is only possible to provide an initaliser to elements in order; they cannot be skipped. What you can do is initialise the array to zero, and assign some of the elements later. Example:

int arr[5]{};
arr[0] = 3;
arr[2] = 5;

or, you can use default initialisation instead:

int arr[5];
arr[0] = 3;
arr[2] = 5;

In which case the elements will have indeterminate values until assigned. Do not ever read indeterminate values; It is not useful and typically results in undefined behaviour.

Upvotes: 1

463035818_is_not_an_ai
463035818_is_not_an_ai

Reputation: 122133

in a way that the index of 3 is 0 and 5 is 2.

That would be 

int arr[5] = {3,0,5,6};

So index 1 is skipped and automatically assigned value by compiler!

You cannot skip elements in the middle, only in the end as in your 

int arr[5] = {3,5,6};

Where the missing elements in the end are initialized with 0.

Note that what you want is possible in C. Example from cppreference:

int n[5] = {[4]=5,[0]=1,2,3,4} // holds 1,2,3,4,5

However this is not (yet?) possible in standard C++.

PS: If you do not care about portability (actually you should) you can study your compilers manual to see if it allows the c-style initialization also in C++.

Upvotes: 5

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