Need help with Bubblesort with random numbers

[grindbert]

hi,
i'm trying to fill an array with random numbers and then sort them via bubblesort. it seems to work so far. the problem is, that i seem to get the same numbers for the same input. somehow the randomness isn't working. anyone an idea why?

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

int main()
{    
    int a, b, c, d, e, f;
    
printf("number of elements from 1 to x:\n");
scanf("%d", &b);
printf("max random number:\n");
scanf("%d", &f);
    int array[b];
    for(a=0; a<b; a++)
    {
        c = rand() %f+1;
        array[a] = c;
    }
    for(a=0; a<b; a++)
    {
        for(d=0; d<b-1; d++)
        {
            if(array[d] > array[d+1])
            {
                e=array[d];
                array[d]=array[d+1];
                array[d+1]=e;
            }
        }
    }
    for(a=0; a<b; a++)
    {
        printf("%d\n", array[a]);
    }
    return 0;
    }

greetings,
grindbert

[Matticus]

You need to seed the random number generator with "srand()".

It's typical to use the current time as a seed, to ensure different values each run. See here for an example: FAQ > Generate random numbers? - Cprogramming.com

[grindbert]

thanks!
i'll look into it.

[laserlight]

You should use names that are descriptive. Generally, single letter variable names are only used for loop/array indices, or in certain computations to correspond to their naming in some mathematical formula. For example, instead of using b to mean "number of elements", you could have used number_of_elements, element_count, num_elements, or something along those lines that give the reader an idea of what it is for.

Next, note that you are creating a variable length array here:

int array[b];

If this works for you, well and good, but note that C implementations are not required to support the feature.

it seems to work so far. the problem is, that i seem to get the same numbers for the same input. somehow the randomness isn't working. anyone an idea why?

You did not call srand to seed the pseudorandom number generator differently on each run of the program.

By the way, it is good to see your effort at proper indentation, but the four printf/scanf calls should have been properly indented too.