Question

Hi!, having trouble with this one,

In this class we use visual studio, C++ language

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Exercise #10 Pointers - Complete the missing 5 portions of part1 (2 additions) and part2 (3 additions)

Part 1 - Using Pointers

int largeArray (const int [], int);
int largePointer(const int * , int);
void fillArray (int * , int howMany);
void printArray (const char *,ostream &, const int *, int howMany);

const int low = 50; const int high = 90;

void main()
{
const int MAX_SIZE = 40;
int info[MAX_SIZE];
int used;
cout << "How many elements in the array? ";
cin >> used;
while ( used <= 0 || used > MAX_SIZE )
{ cout << "Enter a value between 1 and " << MAX_SIZE << "How many elements in the array? ";
cin >> used;
}
fillArray (info,used);
printArray("Array of data",cout,info,used);

cout << "The largest element using subscripts is " << largeArray (info,used) << endl;
cout << "The largest element using pointers is " << largePointer(info,used) << endl; }

//ENDMAIN

void printArray(const char * m,ostream & Out,const int * p, int hm)
{
Out << m << endl;
for(int i = 0; i < hm; i++)
{
Out << p[i] << endl;
}
}
void fillArray(int * p , int howMany) // as parameters, pointers and arrays are one and the same
{ int range = high - low + 1;
srand(time(0));
for( int i = 0; i < howMany; i++)
{
p[i] = rand() % range + low;
}
}
int largeArray(const int data[], int howMany) // use subscripts
{
int largest = 0;
// 1 - WRITE THE CODE TO FIND THE LARGEST NUMBER - USE SUBSCRIPTS TO ACCESS THE ELEMENTS
return largest;
}
int largePointer(const int * data, int howMany) // use pointers
{
int largest = 0;
// 2 - WRITE THE CODE TO FIND THE LARGEST NUMBER - USE POINTERS TO ACCESS THE ELEMENTS
return largest;
}

----------------HINT FOR PART 1--------------------------------------

PART 1 - HINTS AND COMMENTS BELOW...PAY PARTICULAR ATTENTION TO THE IDEA OF ADDRESSES VS POINTERS

int largeArray (const int [], int);
int largePointer(const int * , int);

The above function prototypes both find the largest item in an integer array
The first prototye passes the integer array, but (like all arrays) passes the address of the first element of the array
The second prototype passes a pointer to the first element of the array
...so essentially they are doing the exact same thing in two different ways...ie address vs pointer
...the second int parameter is, of course, the size of the array

void fillArray (int * , int howMany);

The above function prototype (which will load an array with integers) passes a pointer to the array to be filled

void printArray (const char *,ostream &, const int *, int howMany);

The above function prototype will print the contents of an array.
The first parameter is a character pointer, pointer to a string of chars which will be output as a heading
The second parameter is the output stream (cout, in this example) where the output will go
The third parameter is an integer pointer, pointing to an array of integers
The fourth parameter is the size of the array to be printed

const int low = 50; const int high = 90; ...used to randomly select integers in the range of 50- 90

void main()
{
const int MAX_SIZE = 40; ...this forces a limit on the number of integers that we can store in an array
int info[MAX_SIZE];
int used;
cout << "How many elements in the array? ";
cin >> used;
while ( used <= 0 || used > MAX_SIZE ) ...this while forces the user to input a number between 1 and 40
{
cout << "Enter a value between 1 and " << MAX_SIZE << "How many elements in the array? ";
cin >> used;
}

fillArray (info,used); ...NOTICE HERE ...the address of array info is passed
printArray("Array of data",cout,info,used); ...NOTICE HERE ...the address of the string and int * pointer to "info" is passed
...THE ONLY WAY YOU CAN TELL IS BY LOOKING AT THE FUNCTION PROTOTYPES AT THE TOP OF THE PROGRAM!

cout << "The largest element using subscripts is " << largeArray (info,used) << endl;
cout << "The largest element using pointers is " << largePointer(info,used) << endl; }

In the above two CALLS TO the functions (largeArray and largePointer)
...array "info" is passed as an address in the first function call
...array "info" is passed as a pointer in the second function call
The only way you can tell is by looking at the prototypes at the top of this sample!!

//ENDMAIN

void printArray(const char * m,ostream & Out,const int * p, int hm)
{
...notice m is a character pointer,now pointing to the string "Array of data" which is a array of chars
Out << m << endl;
...Out is an ostream...passed as "cout"
for(int i = 0; i < hm; i++) ..."hm" is the howmany alias...ie size of the array
{
Out << p[i] << endl;
... p is an "int *"..ie a pointer to an integer...BUT LIKE ALL POINTERS CAN BE USED AS IF IT WERE AN ARRAY
}
}
void fillArray(int * p , int howMany) // as parameters, pointers and arrays are one and the same
{ int range = high - low + 1;
srand(time(0));
for( int i = 0; i < howMany; i++)
{
p[i] = rand() % range + low;
...p, again, is passed as an "int *" pointer...BUT LIKE ALL POINTERS CAN BE USED AS IF IT WERE AN ARRAY
}
}
int largeArray(const int data[], int howMany) // use subscripts
{
int largest = 0;
// 1 - WRITE THE CODE TO FIND THE LARGEST NUMBER - USE SUBSCRIPTS TO ACCESS THE ELEMENTS
...USE A FOR LOOP AND DATA[i] references, like in the fillArray functions
...TO STORE DATA[i] IN LARGEST
return largest;
}
int largePointer(const int * data, int howMany) // use pointers
{
int largest = 0;
// 2 - WRITE THE CODE TO FIND THE LARGEST NUMBER - USE POINTERS TO ACCESS THE ELEMENTS
...USE A FOR LOOP AND "*DATA" references instead of data[i] references
...TO STORE *DATA IN LARGEST
return largest;
}

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