Question

How to remove duplicate elements from int array using qsort in C

Answer 1

#include <stdio.h>
#include <stdlib.h>
 
int compare(const void *a, const void *b) {
   return ( *(int*)a - *(int*)b );
}
 
int remove_duplicates(int *p, int len) {
	qsort(p, len, sizeof(int), compare);
	
	int j;
	for (int i = j = 0; i < len; i++)
		if (p[i] != p[j]) p[++j] = p[i];
		
	return j + 1;
}
 
int main()
{
	int arr[] = {2, 3, 2, 6, 3, 7, 9, 9};
	
	int len = remove_duplicates(arr, sizeof(arr) / sizeof(arr[0]));
	
	for (int i = 0; i < len; i++) 
	    printf("%d ", arr[i]);
 
	return 0;
}
 

 
/*
run:
 
2 3 6 7 9 
 
*/

 

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