The number of elements in a static array and dynamic array

Question

What is the fastest way to find the number of elements in a static array and dynamic array?

Answer 1

It is not possible to find the number of elements in a dynamically created array. For a non-dynamic array, you can use sizeof(array)/sizeof(type) . However, this is not as useful as it seems:

 void f( int a[] ) { // sizeof(a) will be the size of a pointer, probably 4 } int main() { int a[100]; // sizeof(a)/sizeof(int) will be 100 f( a ); } 

This is because arrays decay into pointers when passed to functions. Therefore, in both cases, you probably need to remember the size of the array and pass it to the functions as a separate parameter. Thus, the function of summing the array (for example) will look like this:

 int sum( int a[], int n ) { int total = 0, i; for ( i = 0; i < n; i++ ) { total += a[i]; } return total; }