help with code, rotating an array

[sadloser]

My code outputs the following array first: 0 1 4 9 16 25
That "rotateList" function outputs this: 25 0 1 4 9 16

What do I fix so that the following outputs instead: 25 16 9 4 1 0
Thanks in advance!


Here's my code:

#include <iostream>
#include <iomanip>
#include <stdlib.h>
#include "apvector.h"

using namespace std;

void printList (const apvector<int> &list);
void squareList (apvector<int> &list);
void rotateList (apvector<int> list);

const int MAX = 6;

int main()
{
	system ("cls");

	apvector<int> data(MAX);

	for (int i = 0; i < MAX; i++)
		data[i] = i;
	cout << "Array initialized: ";
    printList(data);
	system ("pause");

	squareList(data);
	cout << "Array after call of squareList: ";
	printList(data);
	system ("pause");

	rotateList(data);
	cout << "Array after call of roateList: ";
	printList(data);
	system ("pause");

	return 0;
}

void printList (const apvector<int> &list)
{
	for (int index = 0; index < MAX; index++)
		cout << list[index] << "  ";
	cout << endl << endl;
}

void squareList (apvector<int> &list)
{
	for (int index = 0; index < MAX; index++)
		list[index] = list[index] * list[index];
}

void rotateList (apvector<int> list)
{
	int temp = list[MAX - 1];
	for (int i = MAX - 1; i > 0; i--)
		list[i] = list[i - 1];
	list[0] = temp;
	cout << "Inside of rotateList: ";
	printList (list);
}

[histrungalot]

Is the output a typo? 25 16 9 4 0 1 isn't a rotate of 0 1 4 9 16 25. Its reversed with 0 and 1 swapped.
Is this the output you wanted?

$ ./a.out
Array initialized: 0  1  2  3  4  5  

Array after call of squareList: 0  1  4  9  16  25  

Inside of rotateList: 25  0  1  4  9  16  

Array after call of roateList: 25  0  1  4  9  16  

[histrungalot]

Yes, you just forgot to pass by reference for rotateList.

// New prototype
void rotateList (vector<int> &list);  // <-- You didn't have the &

// New function def
void rotateList (vector<int> &list)   // <-- You didn't have the & 

That's it.
You need to pass by ref. such that the modifications you made to list in the rotateList function are done to the data vector. Without the & you just rotated a local copy of data and that is why you didn't see the correct output when you printed in the main().

[sadloser]

That's the thing, 25 0 1 4 9 16 is what outputs with that code up there ^ but the thing is, only 25 is moved to the front. Our teacher wants us to make our code so that the output ends up being 25 16 9 4 1 0 but I'm just stuck now, completely confused.

[histrungalot]

So, you just want to reverse the list?
0 1 4 9 16 25 reversed is what you want 25 16 9 4 1 0.
Do you have to do it a certain way?

[sadloser]

Nope, any way is fine.

[histrungalot]

Is apvector derived from an STL vector?

[sadloser]

I'm actually not sure, I just know apvector is a user defined class.

[cire]

Honestly, it sounds like your instructor screwed up on the output requirements. rotateList does exactly what one would expect it to do (although it might be useful to be able to specifiy a direction,) but supplying a reverseList isn't difficult.

Set an index beg to 0. Set another index end to MAX-1. Then:

while beg < end
{
        swap the elements at those indexes 
        increment beg and decrement end.
}