Bubble sort

Hey guys i'm trying to get the bubble sort to work in my if(choice==2) statement but it's not working right at all. Any ideas?
Thanks!

Code:

#include <iostream>
#include <iomanip>
#include <algorithm>

using namespace std;

int main()
{
    int i,num[20],n,j,choice,tmp;

    cout<< "Please enter 20 integers";
    for (i=0; i<20; i++)
    {
        cout<<"\nEnter next value:";
        cin>>num[i];

    }

    cout<<"\n1.Display original data.\n";
    cout<<"2.Sort the data into descending order\n";
    cout<<"3.Display the sorted data (Only if you've already sorted)\n";
    cout<<"4.Get the address of the first element of array.\n\n";
    cin>>choice;
	
    if (choice==1)
    {

        for (i=0; i<20; i++)
        {
            cout<<"\n"<<num[i]<<endl;
        }
		return 0;
	}
	else if (choice==2)
        {
			n=20;
            for (i=0; i<n; i++)
            {
                for (j=0; j<n-i; j++)
				{
                    if (num[j+1] < num[j])    /* compare the two neighbors */
                    {
                        tmp = num[j];         /* swap a[j] and a[j+1]      */
                        num[j] = num[j+1];
                        num[j+1] = tmp;

                        cout<<"Here are your numbers:"<<tmp<<endl;

                    }
				}
            }
		}
    
}

Overflow. (j=i=19+1)

Soma

Originally Posted by Trckst3

Hey guys i'm trying to get the bubble sort to work in my if(choice==2) statement but it's not working right at all. Any ideas?
Thanks!

Code:

#include <iostream>
#include <iomanip>
#include <algorithm>

using namespace std;

int main() {
    int i,num[20],n,j,choice,tmp;

    cout<< "Please enter 20 integers";
    for (i=0; i<20; i++) {
        cout<<"\nEnter next value:";
        cin>>num[i];

    }

    cout<<"\n1.Display original data.\n";
    cout<<"2.Sort the data into descending order\n";
    cout<<"3.Display the sorted data (Only if you've already sorted)\n";
    cout<<"4.Get the address of the first element of array.\n\n";
    cin>>choice;

    if (choice==1) {

        for (i=0; i<20; i++) {
            cout<<"\n"<<num[i]<<endl;
        }
        return 0;
    } else if (choice==2) {
        n=20;
        for (i=0; i<=n; i++) {
            for (j=i; j<=n; j++) {
                if (num[j+1] < num[j]) {  /* compare the two neighbors */
                    tmp = num[j];         /* swap a[j] and a[j+1]      */
                    num[j] = num[j+1];
                    num[j+1] = tmp;

                    cout<<"Here are your numbers:"<<tmp<<endl;

                }
            }
        }
    }
}

Just cleaning up your formatting there a bit.

The problem is in your two loops. You have to check the extremes and you'll find that you're checking data outside the loop. Changing the '<'s to '<='s should fix the problem. But I haven't run it so I may have gone the wrong direction. That is to say I maybe should have suggested the 'n's in your for statements be 'n-1's. I'm kinda groggy right now, so I can't think.

Also:
You are missing a main loop. How do you expect to enter 1 and then enter 2? That return statement wont play nicely with a loop either.
Case 3 is the same as case 1.
What do you expect number 4 to do? It seems pretty pointless to me.

This should not be there, you need to remove it.

Code:

                        cout<<"Here are your numbers:"<<tmp<<endl;