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Advanced Programming Techniques in C

Using Quick Sort

Explore the use of function pointers and the qsort library function in C to implement quick sort. Understand how qsort uses callbacks to sort an array by calling a user-defined comparison function that handles void pointers, enabling flexible sorting of various data types.

We'll cover the following...

Example program

The code given below illustrates the use of function pointers.

C


# include <stdio.h> 

# include <stdlib.h> 

int fun ( const void * , const void * ) ; 

int main( ) 

{

	int a[ ] = { 17, 6, 13, 12, 2 } ; 

	int i ; 

	qsort ( a, 5, sizeof( int ), fun ) ; 

	for( i = 0 ; i <= 4 ; i++ )	

		printf ( "%d\n", a[ i ] ) ; 

}



int fun ( const void *x, const void *y ) 

{

	int *xx, *yy ; 

	xx = ( int * ) x ; 

	yy = ( int * ) y ; 

	return ( *xx -  *yy ) ; 

}

Explanation

qsort( ) is a library function. It is being used here to arrange numbers in the array, a[ ], in ascending order.

The fourth parameter ...