How do we usually get the length of the array ？

Because the type of each element in the array is the same , The number of bytes in memory is the same , So the total number of bytes divided by the number of bytes occupied by an element is the length of the array .

	int arr={
    1,2,3,4,5,6}
	int len = sizeof(arr)/sizeof(arr[0]); //6

Code up

because , The array passed in is the function parameter , In this function , Array is just a pointer （ Address , When the system runs this function , I don't know how much data storage space the address represented by the array has This is just to tell the function ： The first address of a data storage space ）, So the result is that the pointer variable occupies the memory size

void Reverse(int* arr)
{
    

    int len=sizeof(arr)/(sizeof(arr[0]));
    cout<<sizeof(arr)<<endl;
    cout<<sizeof(arr[0])<<endl;

}