Thread: Can someone explain how this bubble sorting works?

run this

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
#include <string.h>
 
 // use smaller numbers to see what is going on
int main() 
{
 
 
int i;
int array[3] = { };
int j;
int randNum, num = 3, size;
int temp;
srand((int)time(0)); // Seeds Random Numbers
 
 size = sizeof(array)/sizeof(array[0]);
 
 printf("size = %d\n", size);
for (i = 0; i < num ; i++) // Will go through as long as i < 100, i=i+1 every iteration starting at 0.
{
    randNum = rand() %15; // Gets 100 random integers on the interval [1,20]
    array[i] = randNum; // Assigning each of the generated random ints to the array myArray[i]
}
 
  for (i = 0; i < ( num - 1 ); i++) {
      for (j = 0; j < num - i - 1; j++) {
        printf("array[j]%d > array[j+1]%d\n",array[j] , array[j+1] );
        //if first number greater than second number hold it else where.
        if (array[j] > array[j+1]) 
        {
            //here
            temp = array[j];
           // move the smaller one where the bigger one was.
           array[j] = array[j+1];
           printf(" array[j] %d = array[j+1] %d\n",  array[j] , array[j+1]);
           
           array[j+1] = temp;
           //  put the greater one where the smaller one was
           // keep moving next time around the same two will no longer 
           // evalute to 3 > 1, but will be 1 > 3 = no move to the next one. 
        }
      }
    }
 
 
for(i=0; i<num ; i++)
{
    printf("Element: %d\n", array[i]);
 }
 
return 0;
}

oh yes, remember

Code:

int j = 3;
array[j] <--- j sets the element number not value inside of it;
// so array[ j + 1] == what?

if j = 3 , then it is looking into element number 2 : 0,1,2,3,4
so j + 1 then is looking into element number 3 : 0,1,2,3,4
which is one ahead of j.

Code:

array [2] = 3;
array[3] = 1;
           3    >       1
if ( array[j] > array [ j + 1])
// you have to hold that value in a temp so it does not get lost when you over write its place setter/keeper.
  3   =    3
temp = array[j];
now move the lesser 1 to the "left"

                 < -- 1
array[j] = array[j+1];

then put the greater 3 in the lesser place.

                < ---3

array[j+1] = temp;

ending up with
array[j]=1 or array [ 2 ] = 1
array[j+1] = 3 or array [ 3 ] = 3
or
1,3

Originally Posted by csmith03

Thank you! I believe I understand how it works now! The temporary variable holds the higher value. The lower value is then stored into array[j] and after it's moved down in the element, the higher value is now stored in array[j+1], hence the process of moving it up in the 100 elements. Eventually, it will get to t = 100 and then they'll be in ascending order.

in the code,

Code:

for(j=0; j<100+1; j++)

What does

Code:

 j<100+1

mean?

yes because it keep swapping them out lesser takes the greater's place, the greater moves ahead where the lesser was.

bonus lession. to swap the order from , 1,2,3,4,5,6 to 6,5,4,3,2,1

Code:

switch it from this
  if (array[j] > array[j+1]) 

// to this

  if (array[j] < array[j+1])

What does

Code:

 j<100+1

mean?

J < 101

it is

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
#include <string.h>
 
 // use smaller numbers to see what is going on
int main() 
{
 
 
int i, num = 10;

int j;
int randNum, size;
int temp;
srand((int)time(0)); // Seeds Random Numbers
 int array[num]; 
 size = sizeof(array)/sizeof(array[0]);
 
 printf("size = %d\n", size);
for (i = 0; i < num ; i++) // Will go through as long as i < 100, i=i+1 every iteration starting at 0.
{
    randNum = rand() %15; // Gets 100 random integers on the interval [1,20]
    array[i] = randNum; // Assigning each of the generated random ints to the array myArray[i]
}
 printf("num = %d\n", num);
  for (i = 0; i < ( num - 1 ); i++)
  {
      printf(" i %d : num - 1 %d\n", i, (num-1) , i);
      
      for (j = 0; j < num - i - 1; j++) 
      {
          printf(" j %d num - i - 1 %d\n", j, ( num-i-1) );
       
        if (array[j] > array[j+1]) 
        {
             
            temp = array[j];
           
           array[j] = array[j+1];
          
           
           array[j+1] = temp;
         
        }
      }
    }
 
 
for(i=0; i<num ; i++)
{
    printf("Element: %d\n", array[i]);
 }
 
return 0;
}

Originally Posted by csmith03

Interesting... Can I just put 101 instead of 100+1 then?

what is that being used for?

Also, is there a way to add an if statement at the end and remove duplicating numbers in the print statement?

yes. I do not see why you can't you can pretty much put an if statement anywhere within a code block, and
experimentation is a good thing to practice with coding. try it and see.