Sorting Problems

[kas2002]

Hey I need a function that sorts and array of floats. Everyone I have tried to write of find has and incomatible types error I am not asking anyone to write it for me but I need a step in the rite direction on how to implement this into my program thanks

[hint]

Bubble Sort:
Using a loop, compare the first and second elements, and if they're not in the right order, swap them. Repeat this with the second and third elements, and so on, for the rest of the elements((elements - 1) times).
Using another loop, outside this one, repeat the above elements times.

[Cshot]

How are you comparing floats in your if statements?

[Dave_Sinkula]

How about qsort?

#include <stdio.h>
#include <stdlib.h>

int fcmp(const void* a, const void *b)
{
    const float *x = a;
    const float *y = b;
    if(*x > *y)
    {
        return 1;
    }
    if(*x < *y)
    {
        return -1;
    }
    return 0;
}

void show(const float *value, size_t size)
{
    while(size--)
    {
        printf("%14.6f\n", *value++);
    }
}

int main(void)
{
    float array[] = { 1.23F, 0.0F, -15.6F, 23.45, -1.0F, 1.23456F, 5.16F };
    puts("BEFORE");
    show(array,sizeof(array)/sizeof(*array));
    qsort(array,sizeof(array)/sizeof(*array),sizeof(*array),fcmp);
    puts("AFTER");
    show(array,sizeof(array)/sizeof(*array));
    return 0;
}

/* my output
BEFORE
      1.230000
      0.000000
    -15.600000
     23.450001
     -1.000000
      1.234560
      5.160000
AFTER
    -15.600000
     -1.000000
      0.000000
      1.230000
      1.234560
      5.160000
     23.450001
*/

[Hammer]

... and of course, don't forget to read this FAQ entry...

[kas2002]

It might help if I post the errors I keep getting when trying to compile.

invalid types `float **[float]' for array subscript

thats always the error within my sorting function.

[Cshot]

It's even more useful if you post the code block that's giving you problems. But I think it might be caused by indexing an array using a float.

[Hammer]

>>But I think it might be caused by indexing an array using a float.
Yes, you can only use an integral type for array subscripting.

[kas2002]

from scratch so yea and I realized I didn't know how to do it so heres what I have so far I know it is wrong ccause it gives faulty output but anyhoo here it is can anyone help me make it work it doesn't have to be the best just sort the freeking array

void sort(float u[],int n)
{for(int l=0;l<=n;l++) 
 {if (u[l]>u[l-1])
   {u[l]=u[l-1];
    u[l-1]=u[l];
   } 
 }
}

thanx

[Hammer]

You need to use a temporary variable to do a swap.

    u[l]=u[l-1];
    u[l-1]=u[l];

Is the same as
A = B;
B = A;
Can you see the problem?

[kas2002]

I am getting closer. lol
heres what I got now.

void sort(float u[],int n)
{ float temp;

for(int l=0;l<=n;l++) 
 {if (u[l]>u[l-1])
   {temp=u[l];
    u[l]=u[l-1];
    u[l-1]=temp;
   } 
 }
}

it seems to sort some well it moves them around a bit anways.

[Hammer]

To do the sort you'll need a nested loop, traversing the array once won't do the job.

Also, in your code, when you go through the loop the first time, l is set to 0, so you're actually doing this:
>if (u[0]>u[-1])
... which is illegal as you're going outside of the array bounds.


Search the board for some sort code, or, if you want, lookup qsort().