Bubble sort, Selection Sort, Insertion Sort

[amkir100]

mkir100 (1)
So I'm new to C++ and am needing a little help. All feedback is welcome.
I am suppose to create an AList object and then use that AList object to make the following method calls in order:

Read
Print
BubbleSort
Print
Read
Print
InsertionSort
Print
Read
Print
SelectionSort
Print


This is what I have so far:

#include <iostream>

using namespace std;

const int MLS = 50;
typedef int element;
const element SENTINEL = -1;

class AList {
private:

    element items [MLS];
    int size;
    void Swap(int pos1, int pos2); 
    int Read_int();
    element Read_element();

public:
    void Read();
    void Print();
    void BubbleSort();
    void InsertionSort();
    void SelectionSort();
};

int main() {
    AList B;
    B.Read();
    B.Print();
    B.BubbleSort();
    B.InsertionSort();
    B.SelectionSort();
}

void AList::Read() {
    element userval;
    cout<< "Enter elements : ";
    while ((userval!=SENTINEL) && (size<MLS)) {
        items [size] = userval;
        size ++;
    }
}

void AList::Print() {
    for (int i=0;i<size;i++)
        cout<< items[i]<<endl;
}

void AList::BubbleSort() {
    for (int i=0; size-1; i++){
        for (int j=0; j<size-1-i; j++) 
            if (items[j]>items[j+1])
                Swap (j, j+1);
            else 
                ;
    }
}

void AList::Swap(int pos1, int pos2) {
    element temp;
    temp = items[pos2];
    items[pos2]=items[pos1];
    items[pos1]=temp;
}

void AList::InsertionSort() {
    int j;
    bool done;
    for (int i=1; i<size; size++)
       j=i;

    done = false;
    while ((j>=1) && (!done))
        if (items[j] < items[j-1]) {
            Swap (j,j-1);
            j--;
       }
       else 
            done=true;
}

void AList::SelectionSort() {
    int maxpos;
    for (int i = size-1; i<0; i--) {
        maxpos = 0;
        for (int j=1; j<=i; j++)
            if (items[j] < items[maxpos])
                maxpos = j;
            else;

        Swap(maxpos, i);
    }
}

Edit & Run



I don't think that I'm doing it in the order that needs to be done and I'm also having a problem printing everything. Please help!

[2kaud]

I don't think that I'm doing it in the order that needs to be done

Yep. What you're doing is reading the numbers, displaying them and them sorting them in various ways and not displaying the results of any of the sorts.

For main(), consider

int main() {
    AList B;

    B.Read();
    B.Print();
    B.BubbleSort();
    B.Print();

    B.Read();
    B.Print();
    B.InsertionSort();
    B.Print();

    B.Read();
    B.Print();
    B.SelectionSort();
    B.Print();
}

This matches the method calls in post #1.

Note that you have an issue with the member variable size. Where is this being initialised?

[amkir100]

Ok. I'm trying to fix the issue with the variable size.

[amkir100]

I've changed my code a little bit and I'm no longer having any compile issues. However, I can't get the program to run right now.

#include <iostream>
using namespace std;
/*
	
	
	This program will create an AList object and will then make some method calls.
*/
	
const int MLS = 50;
typedef int element;
const element SENTINEL = -1;

class AList {
	private:
		element items [MLS];
		int size;
		void Swap(int pos1,int pos2);
		int Read_element();
		
	public:
		void Read();
		void Print();
		void BubbleSort();
		void InsertionSort();
		void SelectionSort();
			
};

int main (){
        int a;
	AList B;
			
	B.Read();
	B.Print();
	B.BubbleSort();
	B.Print();
			
	B.Read();
	B.Print();
	B.InsertionSort();
	B.Print();
			
	B.Read();
	B.Print();
	B.SelectionSort();
	B.Print();
}

element Read_element() {
	element userval;
	cin>>userval;
	while (!cin.good());
	cout<<"invalid choice please enter a whole number";
	cin.clear();
	cin.ignore(80, '\n');
	cin>>userval;
	return userval;
}

void AList::Read() {
	//PRE: None
	//POST: the N.O. Alist is valid
	//using elements provided by the user
	element userval;
	cout<<"Enter elements,";	
			
	while ((userval!=SENTINEL)&&(size<MLS)) {
		items[size] = userval;
		size ++;
	}
}

void AList::Print() {
	for (int i=0;i<size;i++)
		cout<<items[i]<<endl;
}

void AList::BubbleSort(){
	//PRE: the N.O. List is void
	//Post: the N.O. Alist is unchanged except
	//its elements are now in ascending order
	for (int i=0; size=-1; i++) {
		for (int j=0; j<size-1-i; j++)
			if (items[j]>items[j+1])
				Swap (j,j+1);
			else
				;
	}
}
		
void AList::Swap(int pos1,int pos2) {
	element temp;
	temp = items[pos2];
	items[pos2] = items[pos1];
	items[pos1] = temp;
}
		
void AList::InsertionSort() {
	//Pre: the N.O. Alist is valid
	//Post: the N.O. Alist is unchanged, except that
	//its elements are now in ascending order
			    
	int j;
	bool done;
			
	for (int i = 1; i<size; i++) {
		j=i;
		done=false;
		while ((j>=1)&&(!done))
			if (items[j] < items[j-1]){
		                Swap(j, j-1);
				j-=1;
			}
			else
				done = true;
	}
}

void AList::SelectionSort() {
			
	int maxpos;
		
	for (int i = size - 1; i > 0; i--) {
		maxpos = 0;
		for (int j = 1; j <= i; j++)
			if (items[j] > items[maxpos])
				maxpos = j;
			else
				;
		Swap(maxpos, i);
	}
}

[2kaud]

cout<<"Enter elements,";	
			
	while ((userval!=SENTINEL)&&(size<MLS)) {
		items[size] = userval;
		size ++;
	}

Where do you actually obtain an element value?. Don't you need a call to Read_Element()?

Also

while (!cin.good());

Is not really a good idea as this will loop forever if the state of the cin stream is not good.

for (int i=0; size=-1; i++) {

I don't think you mean this?

If the else clause of an if statement is not needed, rather than just having a ; the else can be omitted.

if (items[j] > items[maxpos])
				maxpos = j;
			else
				;

becomes

if (items[j] > items[maxpos])
				maxpos = j;

[amkir100]

Please explain. I'm not sure I understand.

[2kaud]

Please explain. I'm not sure I understand.

Which don't you understand?

[amkir100]

element Read_element() {
			element userval;
			cout <"Enter a whole number:";
			cin>>userval;
			while (!cin.good());
			cout<<"invalid choice please enter a whole number";
			cin.clear();
			cin.ignore(80, '\n');<
			cin>>userval;
			return userval;

I thought that I had called out Read_element in this statement. I was trying to make it so once the program did run, the only thing that could be entered is a whole number.

public:
void Read_element();
		void Read();
		void Print();
		void BubbleSort();
		void InsertionSort();
		void SelectionSort();

Is that what you mean? I guess that I just need it broken down more.

[2kaud]

Read_element() as you say is trying to ensure that only a whole number could be entered. But this function has to be called to obtain a number.

public:
void Read_element();
		void Read();

What these are are class function declarations. This doesn't actually call the function. Read_element() declared here is not the same Read_element() as defined elsewhere - as the one defined is not a class function.

From post #5, Read_element() is declared as

private:
	element items[MLS];
	int size;
	void Swap(int pos1, int pos2);
	element Read_element();

so the definition should be scoped for the class

element AList::Read_element()

Also Read_element() needs to deal properly with invalid integer input. Consider something like

element AList::Read_element()
{
	element userval;

	while (!(cin >> userval)) {
		cout << "invalid choice please enter a whole number" << endl;
		cin.clear();
		cin.ignore(80, '\n');
	}

	return userval;
}

Within Read() you need to call Read_element() to obtain a number. Something like

void AList::Read()
{
	element userval;
	cout << "Enter elements,";

	for (size = 0; ((userval = Read_element()) != SENTINEL) && (size < MLS); items[size++] = userval);
}

Once you have fixed the bubble sort() issue highlighted in post #5, you should find that the program then works as expected.

PS You don't need to code your own swap function. You can use the c++ swap(), You need to include algorithm. See http://www.cplusplus.com/reference/algorithm/swap/