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  1. /* this program makes an array of pointer to int
  2. and sorts the pointers so that they "point to sorted ints"*/
  3. #include <stdio.h>
  4. #define NB_POS 4
  5.  
  6. /*based on the shellsort algorithm*/
  7. void sort_positions_pointers(int **pt_to_ints, int n){
  8. 	int gap, i, j;
  9. 	int *temp = NULL;
  10. 	/*sorting the pointers*/
  11. 	for(gap = n/2; gap > 0; gap /= 2){ 
  12. 		for(i = gap; i < n; i++){
  13. 			for(j = i-gap; j >= 0 && *(pt_to_ints[j]) > *(pt_to_ints[j + gap]); j -= gap){
  14. 				temp = pt_to_ints[j];
  15. 				pt_to_ints[j] = pt_to_ints[j + gap];
  16. 				pt_to_ints[j + gap] = temp;
  17. 			}
  18. 		}
  19. 	}
  20. }
  21.  
  22. int main(void){
  23. 	/*array of int*/
  24. 	int positions[NB_POS] = {1200, 600, 1300, 2300};
  25. 	/*array of pointers to int*/
  26. 	int *positions_pointers[NB_POS] = {NULL, NULL, NULL, NULL};
  27. 	int i;
  28.  
  29. 	i = 0;
  30. 	/*initialise the array of pointers*/
  31. 	while(i < NB_POS){
  32. 		positions_pointers[i] = &(positions[i]);
  33. 		i++;
  34. 	}
  35.  
  36. 	/*display the unsorted array:*/
  37. 	puts("non sorted array is: ");
  38. 	i = 0;
  39. 	while(i < NB_POS){
  40. 		printf("%d ", *positions_pointers[i]); i++;
  41. 	} puts("");
  42.  
  43. 	sort_positions_pointers(positions_pointers, NB_POS);
  44.  
  45. 	/*display the "sorted pointers to int" array:*/
  46. 	puts("sorted array is: ");
  47. 	i = 0;
  48. 	while(i < NB_POS){
  49. 		printf("%d ", *positions_pointers[i]); i++;
  50. 	} puts("");	
  51.  
  52. 	return 0;
  53. }
Success #stdin #stdout 0s 2168KB
comments (?)
stdin 
Standard input is empty
stdout 
non sorted array is: 
1200 600 1300 2300 
sorted array is: 
600 1200 1300 2300
https://ideone.com/QxHPXC
language:
C (gcc 8.3)
created:
8 years ago
visibility:
secret

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