C++ finding num of elements in a char* array

Question

is there a way to know num of elements in a char* array?

my code is :

char* inputOptions[]={
    NULL,     
    "first sentence",
    "second sentence"}

for(int j=0;j<3;j++)
   cout<<inputOptions[j]<<endl;

and I would like to change '3' to some expression that depends on 'arr'. Is there a way to do so?

ecatmur · Accepted Answer · 2012-09-19 09:15:43Z

5

Yes, you can write

std::distance(std::begin(inputOptions), std::end(inputOptions));

In C++03, use

sizeof inputOptions / sizeof inputOptions[0]

However, in C++11 you would do better to access the array using range for:

for (auto option: inputOptions)
   cout << option << endl;

answered Sep 19, 2012 at 9:15

ecatmur

158k28 gold badges311 silver badges387 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Paul R · Accepted Answer · 2012-09-19 13:39:44Z

2

const char * inputOptions[] = {
    NULL,     
    "first sentence",
    "second sentence" };

const int numOptions = sizeof(inputOptions) / sizeof(inputOptions[0]);

edited Sep 19, 2012 at 13:39

answered Sep 19, 2012 at 9:14

Paul R

214k38 gold badges402 silver badges579 bronze badges

2 Comments

Paul R Over a year ago

Because dynamic arrays are just pointers - the compiler can not know at compile-time how much memory will be allocated to a pointer at run-time.

Pete Becker Over a year ago

The denominator should be sizeof(inputOptions[0]) rather than hard-coded for char*. Doing it that way costs nothing, and makes the code more robust against type changes.

fat-lobyte · Accepted Answer · 2012-09-19 09:14:57Z

1

You can use sizeof() with static arrays, it will give you the size in bytes. If you divide that by the pointer size, you will get the size of the array:

siz = sizeof(inputOptions)/sizeof(char*);

answered Sep 19, 2012 at 9:14

fat-lobyte

1,1991 gold badge10 silver badges16 bronze badges

Collectives™ on Stack Overflow

C++ finding num of elements in a char* array

3 Answers 3

Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related