I have an int array and I need to find the number of elements in it. I know it has something to do with sizeof but I'm not sure how to use it exactly. example
int data2[]={a,b,c,d}; 
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1 Answer
With an array you can do:
int numElements = sizeof(data) / sizeof(data[0]); But this only works with arrays, and won't work if you've passed the array to a function: at that point the array decays to a pointer, and so sizeof will return the size of the pointer.
You'll see this wrapped up in a macro:
#define ARRAY_LENGTH(x) (sizeof (x) / sizeof (x)[0]) 
2 Comments
j_random_hacker
+1. It's a good idea to stick this in a macro, since if you copy and paste it to use it on a different array you can forget to change one of the occurrences of
data: #define lengthof(x) (sizeof (x) / sizeof (x)[0])
Jim Balter
@j_random_hacker I call that ARRAY_LENGTH since that's the only thing it can take the length of.