Integer pointer array sorting in C - c

Question

I have a global integer pointer array, which is created this way
int * array;
array = (int *) malloc(size * sizeof(int));
I also have a sorting algorithm, which is supposed to sort 4 first numbers of the array which size is larger than 4 (16 in this case). sizeOfArray is defined as 4 in this case:
int temp,i,j;
for(i=0;i<sizeOfArray;i++){
for(j=i;j<sizeOfArray;j++){
if(array[i] > array[j]){
temp=array[i];
array[i]=array[j];
array[j]=temp;
}
}
}
Output is really weird for some reason:
Unsorted: 7,6,9,3
Sorted: 3,6,5,1
The weirdest part is if I change algorithm to sort numbers in a descending order, it seems to work:
if(array[i] < array[j])
Unsorted: 10,0,1,8
Sorted: 10,8,1,0
What's causing this? I'm completely lost.

Answer 1

Here is your code wrapped to make an MCVE How to create a Minimal, Complete, Valid Example?:
#include <stdio.h>
#include <stdlib.h>
static void print(int n, int a[n])
{
for (int i = 0; i < n; i++)
printf("%2d", a[i]);
putchar('\n');
}
int main(void)
{
int size = 16;
int *array = (int *) malloc(size * sizeof(int));
array[0] = 7;
array[1] = 6;
array[2] = 9;
array[3] = 3;
int sizeOfArray = 4;
printf("Before:");
print(sizeOfArray, array);
int temp, i, j;
for (i = 0; i < sizeOfArray; i++)
{
for (j = i; j < sizeOfArray; j++)
{
if (array[i] > array[j])
{
temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
}
printf("After: ");
print(sizeOfArray, array);
return 0;
}
The output from this program is:
Before: 7 6 9 3
After: 3 6 7 9
Since this is not the same as the output you get, there must be a difference — a crucial difference. Since you don't show the code that initializes the array, nor show the code that demonstrates that the first 4 elements have the unsorted values, nor show the code that demonstrates the sorted values are wonky, it is not possible to say for certain what is wrong — but the problem is not in the code you show.
I've not fixed the code to check that the memory allocation succeeds; nor have I modified the code to release the allocated space. Both should be done.
The code does use C99 features; it is trivial to revise it not to do so:
static void print(int n, int *a)
{
int i;
for (i = 0; i < n; i++)
and move the definition of sizeOfArray before the assignments.

Answer 2

I am sure this will work for your sorting array...in 2nd iteration sizeofarray-1 will work for loop j...
int temp,i,j;
for(i=0;i<sizeOfArray;i++)
{
for(j=0;j<sizeOfArray-1;j++)
{
if(array[i] > array[j])
{
temp=array[i];
array[i]=array[j];
array[j]=temp;
}
}
}

Answer 3

Let's do some iterations of your code with the values you provide : 7,6,9,3. Also, let's assume that sizeOfArray = 4.
For i = j, your condition will never be executed, because array[i] = array[j].
For i = 0 and j = 1 => 7 > 6 => array = {6, 7, 9, 3}
For i = 0 and j = 2 => 6 < 9 => array = {6, 7, 9, 3}
For i = 0 and j = 3 => 6 > 3 => array = {3, 7, 9, 6}
For i = 1 and j = 2 => 7 < 9 => array = {3, 7, 9, 6}
For i = 1 and j = 3 => 7 > 6 => array = {3, 6, 9, 7}
For i = 2 and j = 3 => 9 > 7 => array = {3, 6, 7, 9}
Thus, I obtained the four first elements of your array sorted correctly (which contains size elements and I assume that size = 16).
If you're not sure about the value of sizeOfArray or size, I suggest you to print them and to check if it's really the value you want.
Hope this helps you.