Sorting arrays need help

doc_watson2007 · #1 23-Oct-2004, 01:48

I am tring to write a program that implements this sort.
Here is the heart of a simple transpsition sort. What are I doing wrong?
********************

CPP / C++ / C Code:

for (i = 0; i < size; ++i)
 for (j = i + 1; j < size; ++j)
    if (arr[i] > arr[j])
       swap(&arr[i], &arr[j]);

********************
thanks for any assistance
USN

CPP / C++ / C Code:

#include <stdio.h>

void swap(int *,int *);

int main(void)

{

int arr[] = { 7, 3, 66, 3, -5, 22, -77, 2} ;
int i, j;


for ( i = 0 ; i < 8; ++i )
	printf("%d ", arr[i]);
	printf("\n");

{

for ( j = i + 1; j < 7; ++j)

	/* Compare Numbers */

if (arr[i] > arr[j])


	/* Display sorted list */

void swap(&arr[i], &arr[j]);

		printf("%d ", arr[j]);
		printf("\n");

return 0;
}
}

/*Unordered data 7 3 66 3 -5 22 -77 2
First pass -77 7 3 66 3 -5 22 2
Second pass -77 -5 7 3 66 3 2 22
Third pass -77 -5 2 7 3 66 3 22
Fourth pass -77 -5 2 3 7 3 66 22
Fifth pass -77 -5 2 3 3 7 22 66
Sixth pass -77 -5 2 3 3 7 22 66
Seventh pass -77 -5 2 3 3 7 22 66 */

dsmith · #2 23-Oct-2004, 07:14

Hi doc_watson2007. Welcome to GIDForums.

There are several problems that I see with your program, but probably the most noticeable is the formatting.

The basic structure of your program should be grouped more like:

CPP / C++ / C Code:

  for ( i = 0 ; i < 8; ++i ){     //Notice the beginning bracket here
    printf("%d ", arr[i]);
    printf("\n");
    for ( j = i + 1; j < 7; ++j){   //Again a beginning bracket
      /* Compare Numbers */
      if (arr[i] > arr[j])   //No bracket needed as only a single command follows.
        swap(&arr[i], &arr[j]);   //You need to write this function.
    }
  }
  return 0;  //Should not be inside the for loop.
}

Notice that the indenting helps to identify which code should be in which loop.

Your print statements are also slightly misplaced I believe. You should sort the entire structure as shown above and then do a completely new loop which prints the entire array.

Also, you need to write the swap function. The basis of which is:

CPP / C++ / C Code:

  temp = a;
  a = b;
  b = temp;

HTH.

doc_watson2007 · #3 23-Oct-2004, 13:23

Quote:

Originally Posted by dsmith

Hi doc_watson2007. Welcome to GIDForums.

There are several problems that I see with your program, but probably the most noticeable is the formatting.

The basic structure of your program should be grouped more like:

CPP / C++ / C Code:

  for ( i = 0 ; i < 8; ++i ){     //Notice the beginning bracket here
    printf("%d ", arr[i]);
    printf("\n");
    for ( j = i + 1; j < 7; ++j){   //Again a beginning bracket
      /* Compare Numbers */
      if (arr[i] > arr[j])   //No bracket needed as only a single command follows.
        swap(&arr[i], &arr[j]);   //You need to write this function.
    }
  }
  return 0;  //Should not be inside the for loop.
}

Notice that the indenting helps to identify which code should be in which loop.

Your print statements are also slightly misplaced I believe. You should sort the entire structure as shown above and then do a completely new loop which prints the entire array.

Also, you need to write the swap function. The basis of which is:

CPP / C++ / C Code:

  temp = a;
  a = b;
  b = temp;

HTH.

Thanks.
Now I am getting a undef ref for swap(&arr[i], &arr[j]);

/* Compare Numbers */

if (arr[i] > arr[j])
swap(&arr[i], &arr[j]);

}
}
void swap(int *, int *);

{
int tmp;

tmp = i;
i = j;
j = tmp;
}

return 0;
}

nkhambal · #4 23-Oct-2004, 14:49

function definition is problem. Are you defining your swap function code inside main() ? Is yes, then you can not do that in C. You have to move the function code outside main() either before or after. Secondly, You are referencing i and j inside swap function without declaring them. Also, i & j are pointers variables and not regular variables. So you can not use

CPP / C++ / C Code:

tmp=i;
i = j;
j = tmp;

it should be

CPP / C++ / C Code:

void swap(int *i, int *j)         //removed the ; here
{
int tmp;

tmp = *i;
*i = *j;
*j = tmp;
}

In case you are defining your swap function code after main(). To be able to compile without errors, You need to prototype your swap function before main().Following should be your program structure.

CPP / C++ / C Code:

#include<stdio.h>

void swap(int *, int *);

main()
{

Your main fuction code...

}

swap (int *i, int *j)
{

swap function code.

}

Use code tags when you are posting code.

doc_watson2007 · #5 01-Nov-2004, 01:02

Quote:

Originally Posted by nkhambal

function definition is problem. Are you defining your swap function code inside main() ? Is yes, then you can not do that in C. You have to move the function code outside main() either before or after. Secondly, You are referencing i and j inside swap function without declaring them. Also, i & j are pointers variables and not regular variables. So you can not use

CPP / C++ / C Code:

tmp=i;
i = j;
j = tmp;

it should be

CPP / C++ / C Code:

void swap(int *i, int *j)         //removed the ; here
{
int tmp;

tmp = *i;
*i = *j;
*j = tmp;
}

In case you are defining your swap function code after main(). To be able to compile without errors, You need to prototype your swap function before main().Following should be your program structure.

CPP / C++ / C Code:

#include<stdio.h>

void swap(int *, int *);

main()
{

Your main fuction code...

}

swap (int *i, int *j)
{

swap function code.

}

Use code tags when you are posting code.

Thanks . This is what I have so far still head banging.

CPP / C++ / C Code:

#include <stdio.h>

void swap(int *, int *);

int main(void)
{

/* main function code... */

int arr[] = {7, 3, 66, 3, -5, 22, -77, 2};

int i, j;

printf ("\nArray Unordered data:\n");

	for (i = 0; i < 8; ++i)
	
	 printf("%d ", arr[i]);
	  printf("\n\n");

	   for ( i = 0; i < 8-1; ++i )
			for ( j = 1; j < 8-i; ++j )
			printf("%d ", arr[j]);
			printf("\n");

			  if ( arr[i-1] > arr[j] )
				 swap( arr[i-1], arr[j] );
}

/* swap function code. */

void swap(int *i,int *j)

{
int tmp;

tmp = i;
i = j;
j = tmp;
}

dsmith · #6 01-Nov-2004, 07:21

Hi doc_watson2007. Please, please, please use [c] & [/c], when you post C (or C++) code to this forum. Also, I think that this is a must read for proper formatting. Indentation and the such may seem like a little thing, but it is extremely important to readability and will help you catch errors in your code.

The problem with your code is that you keep switching between a swap function that takes two integer pointers and a swap function that takes two ingegers. Right now, you are passing the integers, but your function is looking for pointers. You must pass by pointer, in order for your swap function to act upon the actual values and not just a copy of the values. Therefore, this line should be changed to pass an address like you originally had:

CPP / C++ / C Code:

swap( &arr[i-1], &arr[j] );

Your swap function is correct in header definition, but remember, since you are using pointers to integers, you need to use * notation to specify the value of the what the pointer points to. Check out the differences between your swap function and nkhambal's swap function. Hint: his is correct.

Good luck!
[

nkhambal · #7 01-Nov-2004, 14:46

Another problem with your program is the for loops you are using for sorting the array. You are not using { } brackets after each "for" statment. If you do not use {} brackets after any of your loop conditions, only the statment next to your loop condition will be executed.

Following lines of code

CPP / C++ / C Code:

for ( i = 0; i < 8-1; ++i )
      for ( j = 1; j < 8-i; ++j )
      printf("%d ", arr[j]);
      printf("\n");

        if ( arr[i-1] > arr[j] )
            swap( arr[i-1], arr[j] );

Will effectively only execute first printf in the inner for loop. You need to use {} properly in your loops to get the required results.

Also, there is a problem with the sort logic in your for loops. It should be.

CPP / C++ / C Code:

for ( i = 0; i < 8; ++i )
  {
      for ( j = 1; j < 8-i; ++j )
       {
        printf("%d ", arr[j]);
        printf("\n");

        if ( arr[j] > arr[j+1] )
	         swap( &arr[j], &arr[j+1] );
        }
  }

You can add another for loop after the sorting operation is complete, to print the sorted array, instead of printing array elements inside sorting loops (unless being used for debugging purpose.)

Good luck.

doc_watson2007 · #8 07-Nov-2004, 23:20

Quote:

Originally Posted by nkhambal

Another problem with your program is the for loops you are using for sorting the array. You are not using { } brackets after each "for" statment. If you do not use {} brackets after any of your loop conditions, only the statment next to your loop condition will be executed.

Following lines of code

CPP / C++ / C Code:

for ( i = 0; i < 8-1; ++i )
      for ( j = 1; j < 8-i; ++j )
      printf("%d ", arr[j]);
      printf("\n");

        if ( arr[i-1] > arr[j] )
            swap( arr[i-1], arr[j] );

Will effectively only execute first printf in the inner for loop. You need to use {} properly in your loops to get the required results.

Also, there is a problem with the sort logic in your for loops. It should be.

CPP / C++ / C Code:

for ( i = 0; i < 8; ++i )
  {
      for ( j = 1; j < 8-i; ++j )
       {
        printf("%d ", arr[j]);
        printf("\n");

        if ( arr[j] > arr[j+1] )
	         swap( &arr[j], &arr[j+1] );
        }

  }

You can add another for loop after the sorting operation is complete, to print the sorted array, instead of printing array elements inside sorting loops (unless being used for debugging purpose.)

Good luck.

I have started from the beginning, this is what I have accomplish so far. I am still having probs with it printing the 2 thru 8 arrays. Hopefully I post this correctly.

CPP / C++ / C Code:

#include <stdio.h>

#define N 8

void order(int *p, int *q);

int main(void)
{
int    a[] = {7, 3, 66, 3, -5, 22, -77, 2}; 
int    i; 
int    j; 
int    k; 

   /* main program */

printf("\n   Unordered data:");
for (k = 0; k < N; ++k)  
	printf("%6d", a[k]);  
	    printf("\n");        

		for (i = 0; i < N; ++i) 
						
			for (j = i + 1; j < N; ++j)
								
	/*Compare Data*/
				
if (a[i] > a[j])
	order(&a[i], &a[j]);
		printf("     After pass %d:", ++i);
	for (k = 0; k < N; ++k)
		printf("%6d", a[k]);
			printf("\n");
return 0;
}
void order(int *p, int *q)

/* Swap Function* /
{
   int tmp;

   tmp = *p;
   *p = *q;
   *q = tmp;
}

nkhambal · #9 08-Nov-2004, 00:14

I don't see any problem with your code, except one typo which is causing you entire function definition of order to be commented out.

Following line had problem

CPP / C++ / C Code:

/* Swap Function* /

It should be

CPP / C++ / C Code:

/* Swap Function */

Following code complied correctly and executed and given proper result to me.

CPP / C++ / C Code:

#include <stdio.h>

#define N 8

void order(int *p, int *q);

int main(void)
{
int    a[] = {7, 3, 66, 3, -5, 22, -77, 2};
int    i;
int    j;
int    k;

   /* main program */

printf("\n   Unordered data:");
for (k = 0; k < N; ++k)
  printf("%6d", a[k]);
      printf("\n");

    for (i = 0; i < N; ++i)

      for (j = i + 1; j < N; ++j)

  /*Compare Data*/

if (a[i] > a[j])
  order(&a[i], &a[j]);
    printf("     After pass %d:", ++i);
  for (k = 0; k < N; ++k)
    printf("%6d", a[k]);
      printf("\n");
return 0;
}
void order(int *p, int *q)

/* Swap Function */

{
   int tmp;

   tmp = *p;
   *p = *q;
   *q = tmp;
}

Following was the output when I executed it.

Quote:

Unordered data: 7 3 66 3 -5 22 -77 2
After pass 9: -77 -5 2 3 3 7 22 66

The reason its printing only pass 9 is because you have not used {} after if statement. That why if is only executing order function calls specified number times by two for loops. When it is out of for loops, its executing your printf statment. If you want print to be executed in each pass you need to use {} properly. I would like you to try it out yourselve.

WaltP · #10 08-Nov-2004, 00:21

Quote:

Originally Posted by doc_watson2007

I have started from the beginning, this is what I have accomplish so far. I am still having probs with it printing the 2 thru 8 arrays. Hopefully I post this correctly.

Your bracketting and formatting makes your program very difficult to follow. Check the format tutorial...

CPP / C++ / C Code:

#include <stdio.h>
#define N 8
void order(int *p, int *q);

int main(void)
{
    int    a[] = {7, 3, 66, 3, -5, 22, -77, 2}; 
    int    i; 
    int    j; 
    int    k; 

       /* main program */

    printf("\n   Unordered data:");
    for (k = 0; k < N; ++k)  
    {
        printf("%6d", a[k]);  
    }
    printf("\n");        

    for (i = 0; i < N; ++i) 
    {
        for (j = i + 1; j < N; ++j)
        {
            /*Compare Data*/
            if (a[i] > a[j])
            {
                order(&a[i], &a[j]);
            }
        }
    }
    printf("     After pass %d:", ++i);
    for (k = 0; k < N; ++k)
    {
        printf("%6d", a[k]);
    }
    printf("\n");
    return 0;
}

/* Swap Function* /
void order(int *p, int *q)
{
   int tmp;

   tmp = *p;
   *p = *q;
   *q = tmp;
}

Now add some comments so you can keep track of what sections do what. You may be able to find your problem easily now.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Rate This Thread
Rate This Thread:

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Deleting elements of arrays C++	the_crazyman	C++ Forum	25	30-May-2008 08:27
Knight tour (arrays help needed)	dilmv	C++ Forum	7	18-Oct-2004 15:31
problem with arrays	melas	C Programming Language	5	12-Oct-2004 05:18
sorting question	fj8283888	C Programming Language	1	13-Apr-2004 21:42
need help with passing 3 arrays into a function	tommy69	C Programming Language	14	07-Apr-2004 01:22

Sorting arrays need help

sorting arr

sorting arrays

array swapping