C++ bubble sort 2d array error.

Steviemoyne

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'm having a problem with the following code where 19 gets put in when it's not there and you loose one of the numbers in the array because of it.

The problem seems to happen when the bubble sort does its stuff...

I can't for the life of me figure out what is causing the 19...and when there actually is a 19 in the array TWO appear xD

Any help would be appreciated.

#include<iostream.h>
#include<conio.h>
#include<iomanip.h>
#include<stdlib.h>
//Name:
//Author:
//Date:
void generate(void);
void extract(void);
void bubble_sort(void);
void pushback(void);
void display2d(void);

int arr2d[4][4], arr1d[16];
main()
{
 generate();                //call generate() to populate the 2d array
 display2d();                //display the unsorted 2d array
 extract();             //pull nums out of 2d into 1d array
 bubble_sort();         //use bubble sort to sort in 1d array
 pushback();            //push nums back into 2d from sorted 1d array
 display2d();           //show sorted 2d array on screen
}
//------------------------------------------------------------------------
void generate()
{
 int x,y;
 randomize();

 for(x=0;x<4;x++)
 {
  for(y=0;y<4;y++)
   {
    arr2d[x][y]= random(50)+1; //pick random number & store in 2d array
   }
  }
}        //end of generate function
//------------------------------------------------------------------------
void extract()
 {
  int x,y,cnt=0;

 for(x=0;x<4;x++)
 {
  for(y=0;y<4;y++)
   {
    arr1d[cnt] = arr2d[x][y];   //take from 2d array & put into 1d array
    cout<<arr1d[cnt]<<" ";      //show value on screen
    cnt++;                      //increase index into 1d array by 1
   }
 }
 cout<<endl;
}            //end of extract function
//------------------------------------------------------------------------
void bubble_sort()
{
      int i,x, j, flag = 1;    // set flag to 1 to start first pass
      int temp;                // holding variable

    while(flag == 1)
     {
          flag = 0;
          for (j=0; j < 16; j++)
           {
               if (arr1d[j+1] < arr1d[j])  // ascending order simply changes to <
              {
                    temp = arr1d[j];       // swap elements
                    arr1d[j] = arr1d[j+1];
                    arr1d[j+1] = temp;
                    flag = 1;              // indicates that a swap occurred.
               }
           }
     }
}
//------------------------------------------------------------------------
void pushback()
{
 int x,y,cnt=0;

 for(x=0;x<4;x++)
 {
  for(y=0;y<4;y++)
   {
    arr2d[x][y] = arr1d[cnt];  //take number from 1d array & put into 2d
    cnt++;                     //increase index into 1d array
   }
 }
}
//------------------------------------------------------------------------
void display2d()
{
 int x,y;
  cout<<endl;

 for(x=0;x<4;x++)
 {
  for(y=0;y<4;y++)
   cout<<setw(4)<<arr2d[x][y]; //output element off array in field width 4

   cout<<endl;
 }
 cout<<endl;

getch();
}
//------------------------------------------------------------------------

scotty_irish

set your loop from 0 to 15, not 16!as then you access an non existant 17th element.

easy mistake to make!

good luck!

Steviemoyne

scotty_irish wrote: »

set your loop from 0 to 15, not 16!as then you access an non existant 17th element.

easy mistake to make!

good luck!

You sir. Are a genius.

Thanks very much!