Stabilizing the standard library qsort?

by

No, you cannot rely on that unfortunately. Let’s assume you have the array (two fields in each record used for checking but only first field used for sorting):

B,1
B,2
A,3

A non-stable sort may compare B,1 with A,3 and swap them, giving:

A,3
B,2
B,1

If the next step were to compare B,2 with B,1, the keys would be the same and, since B,2 has an address less than B,1, no swap will take place. For a stable sort, you should have ended up with:

A,3
B,1
B,2

The only way to do it would be to attach the starting address of the pointer (not its current address) and sort using that as well as the other keys. That way, the original address becomes the minor part of the sort key so that B,1 will eventually end up before B,2 regardless of where the two B lines go during the sorting process.

More Related Contents:

  1. How to qsort an array of pointers to char in C?
  2. Need help using qsort with an array of structs
  3. Who can help me with a key list in C?
  4. Hash function for sorting 100 or more integar numbers [closed]
  5. The Definitive C Book Guide and List
  6. Read/write files within a Linux kernel module
  7. Why does the order of ‘-l’ option in gcc matter? [duplicate]
  8. Hide password input on terminal
  9. Must declare function prototype in C? [duplicate]
  10. returning multiple values from a function [duplicate]
  11. C: unary minus operator behavior with unsigned operands
  12. What are the differences between strtok and strsep in C
  13. Is there an alternative sleep function in C to milliseconds?
  14. How do I execute a Shell built-in command with a C function?
  15. Unable to free const pointers in C
  16. How do you set only certain bits of a byte in C without affecting the rest?
  17. CPU and Data alignment
  18. Finding consecutive bit string of 1 or 0
  19. “UNDEFINED REFRENCE TO clrscr();” [duplicate]
  20. scanf(“%c”) call seems to be skipped
  21. How to properly flush stdin in fgets loop
  22. Which variable types/sizes are atomic on STM32 microcontrollers?
  23. Why does this code print two times? [duplicate]
  24. Does stdlib’s rand() always give the same sequence?
  25. Difference between surface and texture (SDL / general)
  26. How can I create C header files [closed]
  27. Comma operator in condition of loop in C
  28. Difference between pointer to pointer and pointer to array?
  29. How do I access local C variable in arm inline assembly?
  30. literal constant vs variable in math library

Leave a Comment