receipt takes an array of Items as its first parameter, and an int as a second parameter. The second parameter specifies the number of elements in the array
( As a suggestion I would name the Item object or struct with singular "Item" rather than plural "Items". The array of Item's I would name as shopping_cart[], catalogue[] or inventory[] or item_array[] etc. then say size_inventory, array_size etc )
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void receipt( Item items[], int elements)
{
...
}
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void receipt( Item shopping_cart[], int no_of_items)
{
...
}