Generic quick sort
While comparing in generic quick sort , void * is to be converted to char * and comparator and swap functions would be provided by the caller.
/* C implementation QuickSort */
#include<stdio.h>
int cmp(const void *c1, const void *c2)
{
int a = *(const int*)c1;
int b = *(const int*)c2;
if (a > b) return 1;
if (a < b) return -1;
return 0;
}
void swap(void *c1, void *c2)
{
int c = *(int*)c1;
*(int*)c1 = *(int*)c2;
*(int*)c2 = c;
}
/* This function takes last element as pivot, places
the pivot element at its correct position in sorted
array, and places all smaller (smaller than pivot)
to left of pivot and all greater elements to right
of pivot */
int partition (void * arr,int size , int low, int high)
{
int pivot = high; // pivot
int i = (low – 1); // Index of smaller element
for (int j = low; j <= high- 1; j++)
{
// If current element is smaller than or
// equal to pivot
//if (arr[j] <= pivot)
if (cmp((char*)arr + pivot * size, (char*)arr + j * size) > 0)
{
i++; // increment index of smaller element
//swap(&arr[i], &arr[j]);
swap((char*)arr + i * size, (char*)arr + j * size);
}
}
//swap(&arr[i + 1], &arr[high]);
swap((char*)arr + (i+1) * size, (char*)arr + high * size);
return (i + 1);
}
/* The main function that implements QuickSort
arr[] –> Array to be sorted,
low –> Starting index,
high –> Ending index */
void quickSort(void * arr,int size , int low, int high)
{
if (low < high)
{
/* pi is partitioning index, arr[p] is now
at right place */
int pi = partition(arr, size, low, high);
// Separately sort elements before
// partition and after partition
quickSort(arr, size,low, pi – 1);
quickSort(arr, size ,pi + 1, high);
}
}
/* Function to print an array */
void printArray(int arr[], int size)
{
int i;
for (i=0; i < size; i++)
printf(“%d “, arr[i]);
printf(“\n”);
}
// Driver program to test above functions
int main()
{
int arr[] = {10, 7, 8, 9, 1, 5};
int n = sizeof(arr)/sizeof(arr[0]);
quickSort(arr, 4,0, n-1);
printf(“Sorted array: \n”);
printArray(arr, n);
return 0;
}
Code to know direction in which stack grows:
void func(int *p) {
int i;
if (!p)
func(&i);
else if (p < &i)
printf(“Stack grows upward\n”);
else
printf(“Stack grows downward\n”);
}
func(NULL);
These Questions is mainly asked in Adobe Illustrator team interview.