Sorting an Array with Selection Sort - c

Question

#include<stdio.h>
#include <time.h>
int selectionSort(int data[], int count)
{
int a,b;
int tmp;
int minimum;
for(a=0; a<count-1;a++){
minimum = a;
for(b=a+1;b<count;b++){
if(data[minimum]>data[b]) {
minimum = b;
}
}
tmp = data[a];
data[a]=data[minimum];
data[minimum]=tmp;
}
return 0;
}
int main(){
int randomarray[10];
int i;
int k;
srand(time(NULL));
for(i=1; i<=10; i++){
randomarray[i]=rand()%100;
selectionSort(randomarray[i], k = 10 );
printf("%d\n",randomarray[i]);
}
return 0;
}
I am trying to create a program that sorts an array of random integers. I think there is a problem with the declaration of my function, but I am not used to using C. The errors are shown below:
semihosting_example.c:13:5: warning: implicit declaration of function 'srand' [-Wimplicit-function-declaration]
semihosting_example.c:15:5: warning: implicit declaration of function 'rand' [-Wimplicit-function-declaration]
semihosting_example.c:16:5: warning: passing argument 1 of 'selectionSort' from incompatible pointer type [enabled by default]
semihosting_example.c:6:6: note: expected 'int *' but argument is of type 'int (*)[10]'ing_example.c:6:6: note: expected 'int *' but argument is of type 'int (*)[10]

Answer 1

Here's the updated code with the appropriate HEADERS. I am trying to create a function with an array that calls the function with an array:
#include<stdio.h>
#include <time.h>
#include<stdlib.h>
int selectionSort(int (*)[10], int count)
{
int a,b;
int tmp;
int minimum;
for(a=0; a<count-1;a++){
minimum = a;
for(b=a+1;b<count;b++){
if(data[minimum]>data[b]) {
minimum = b;
}
}
tmp = data[a];
data[a]=data[minimum];
data[minimum]=tmp;
}
return 0;
}
int main(){
int randomarray[10];
int i;
int k;
srand(time(NULL));
for(i=1; i<=10; i++){
randomarray[i]=rand()%100;
selectionSort(randomarray[i], k = 10 );
printf("%d\n",randomarray[i]);
}
return 0;
}

Answer 2

Here's a revised version of your program:
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
static void selectionSort(int data[], int count)
{
for (int a = 0; a < count - 1; a++)
{
int minimum = a;
for (int b = a + 1; b < count; b++)
{
if (data[minimum] > data[b])
minimum = b;
}
int tmp = data[a];
data[a] = data[minimum];
data[minimum] = tmp;
}
}
int main(void)
{
int randomarray[10];
srand(time(NULL));
for (int i = 0; i < 10; i++)
randomarray[i] = rand() % 100;
printf("Before:\n");
for (int i = 0; i < 10; i++)
printf("%d: %d\n", i, randomarray[i]);
selectionSort(randomarray, 10);
printf("After:\n");
for (int i = 0; i < 10; i++)
printf("%d: %d\n", i, randomarray[i]);
return 0;
}
When run, it produces output such as:
Before:
0: 73
1: 63
2: 73
3: 80
4: 28
5: 19
6: 63
7: 96
8: 82
9: 46
After:
0: 19
1: 28
2: 46
3: 63
4: 63
5: 73
6: 73
7: 80
8: 82
9: 96
Note that it prints the array before sorting as well as afterwards so that you can tell whether it sorted correctly.
The code doesn't use k; it declares variables as late as possible.
If you replace the line:
selectionSort(randomarray, 10);
with:
selectionSort(&randomarray, 10);
you get the error messages:
$ gcc -O3 -g -std=c11 -Wall -Wextra -Werror -Wmissing-prototypes -Wstrict-prototypes \
> sort53.c -o sort53
sort53.c: In function ‘main’:
sort53.c:32:19: error: passing argument 1 of ‘selectionSort’ from incompatible pointer type [-Werror=incompatible-pointer-types]
32 | selectionSort(&randomarray, 10);
| ^~~~~~~~~~~~
| |
| int (*)[10]
sort53.c:5:31: note: expected ‘int *’ but argument is of type ‘int (*)[10]’
5 | static void selectionSort(int data[], int count)
| ~~~~^~~~~~
$
That's from GCC 10.1.0, but it is very similar to the error messages posted in the question. If you instead replace the call with:
selectionSort(randomarray[0], 10);
then the error messages are:
sort53.c: In function ‘main’:
sort53.c:32:30: error: passing argument 1 of ‘selectionSort’ makes pointer from integer without a cast [-Werror=int-conversion]
32 | selectionSort(randomarray[0], 10);
| ~~~~~~~~~~~^~~
| |
| int
sort53.c:5:31: note: expected ‘int *’ but argument is of type ‘int’
5 | static void selectionSort(int data[], int count)
| ~~~~^~~~~~
cc1: all warnings being treated as errors