Cocktail sorting algorithm issue

[Eternity[LK]]

Hello :)
This is my first post on daniweb forum and I hope this site will help me improve. I'm a first year college student in computer science, and I've only recently started C++. This means that code posted by me might seem very lousy and /or unprofessional.
I have got the program to work, however, there is 1 issue I need help with.

Purpose of the program: Sorting an array of n variables in ascending order, by using cocktail sorting algorithm.

How my program works:
1. User enters the n value
2. array with n elements is generated
3. array is shown on the screen
4. array is sorted
5. sorted array is shown to the user.

The problem: When array, which is sorted already, is shown on the screen, the index of all array elements is by 1 bigger than it should be, the last array element is not shown, and 0 is shown in the place of first element.

Example:
Array1 = 1 7 5 6 3 4 2
Array2 = 0 1 2 3 4 5 6

#include <conio.h>
#include <iostream.h>
#include <stdlib.h>

void swap(int& a, int& b);

int input();
void generation();
void show();

int i,j,a[50],n;

void main(){
	randomize();
   input();
   generation();
	show();
   for(i=0; i<n; i++){
   	if(a[i]> a[i+1]){
      	swap(a[i],a[i+1]);
         for(j=i; j>0; j--){
         	if(a[j-1]>a[j]){
            	swap(a[j-1],a[j]);
            }else{break;}
         }
      }
   }
	show();
	getch();
}

int input(){
	do{cout<<"Please enter the number of elements (1-30): ";
   cin>>n;}while(n<1 || n>30);
   return n;
}

void generation(){
	for(i=0;i<n;i++){
   	a[i]=random(99)+1;
   }
}

void show(){
	for(i=0;i<n;i++){
		cout<<a[i]<<"\t";
	}
   cout<<"\n\n\n";
}

void swap(int& a, int& b){
	int pag;
   pag=a;
   a=b;
   b=pag;
}

[Perveance]

Hello,

just a little change in your code:

#include <conio.h>
#include <iostream.h>
#include <stdlib.h>

void swap(int& a, int& b);

int input();
void generation();
void show();

int i,j,a[50],n;

void main(){
	randomize();
	input();
	generation();
	show();
	
	for(i=0; i<(n-1); i++) 
	{
		if (a[i]> a[i+1])
		{
			swap(a[i],a[i+1]);
			for(j=i; j>0; j--)
			{
				if(a[j-1]>a[j]) { 
					swap(a[j-1],a[j]);
				}
				else
				{
					break;
				}
			}
		}
	}
	
	show();
	getch();
}

int input(){
	do {
		cout<<"Please enter the number of elements (1-30): ";
		cin>>n;
	}	while (n<1 || n>30);
	return n;
}

void generation(){
	for(i=0;i<n;i++){
   	a[i]=random(99)+1;
   }
}

void show(){
	for(i=0;i<n;i++){
		cout<<a[i]<<"\t";
	}
   cout<<"\n\n\n";
}

void swap(int& a, int& b){
	int pag;
	pag=a;
	a=b;
	b=pag;
}

[Perveance]

Eternity[LK], if you want to understand your mistake, you can change show() function like this:

void show(){
	for(i=0;i<50;i++){
		cout<<a[i]<<"\t";
	}
   cout<<"\n\n\n";
}

and you will realize why 0 is shown in the place of first element.

[mrnutty]

You don't have to manipulate the array after being sorted.

You can use a for loop to start from 1 to the array size to show the array. This would disclude the last element. Of course you need to see a 0 at the beginning, so before the for loop just show a 0.

[Perveance]

Eternity[LK] , your algorithm sorts (n+1) elements, not n. The (n+1)-element is always 0, because you use static memory allocation.

Try my version of your code, it works correctly and sorts only n elements.

[Eternity[LK]]

Thank you everyone. Problem was solved and program is working well now.