Standard C library provides qsort function that can be used for sorting an array. Following is the prototype of qsort() function. // Sort an array of any type. The parameters are base // address of array size of array and pointer to // comparator function void qsort (void* base size_t num size_t size int (*comparator)(const void* const void*));
It requires a pointer to the array the number of elements in the array the size of each element and a comparator function. We have discussed qsort comparator in detail ovdje . C ++ Standardna biblioteka pruža sličnu funkciju sorta () koja je nastala u STL. Razgovarali smo o C ++ sortiranju ovdje . Following are prototypes of C++ sort() function. // To sort in default or ascending order. template void sort(T first T last); // To sort according to the order specified // by comp. template void sort(T first T last Compare comp);
The order of equal elements is not guaranteed to be preserved. C++ provides std::stable_sort that can be used to preserve order. Usporedba s QSort i Sort () 1. Pojedinosti o implementaciji: Kao što ime sugerira da QSORT funkcija koristi algoritam QuickSort za sortiranje zadanog niza, iako C standard ne zahtijeva da implementira QuickSort. Funkcija sortiranja C ++ koristi Introsort koji je hibridni algoritam. Različite implementacije koriste različite algoritme. Na primjer, biblioteka GNU Standard C ++ koristi algoritam hibridnog sortiranja u trodijelu: Introsort se prvo izvodi (Introsort je hibrid sortiranja Quicksort-a i HEAP-a) nakon čega slijedi vrsta umetanja na rezultat. 2. Složenost: C Standard ne govori o svojoj složenosti QSORT -a. Novi standard C ++ 11 zahtijeva da složenost vrsta o (nlog (n)) u najgorem slučaju. Prethodne verzije C ++, kao što je C ++ 03, omogućuju mogući najgori scenarij O (n^2). Trebala je biti samo prosječna složenost (n log n). 3. Vrijeme trčanja: STL’s sort ran faster than C’s qsort because C++’s templates generate optimized code for a particular data type and a particular comparison function. STL’s sort runs 20% to 50% faster than the hand-coded quicksort and 250% to 1000% faster than the C qsort library function. C might be the fastest language but qsort is very slow. When we tried to sort one million integers on C++14 Time taken by C qsort() was 0.247883 sec and time taken by C++ sort() was only 0.086125 sec CPP // C++ program to demonstrate performance of // C qsort and C++ sort() algorithm #include using namespace std; // Number of elements to be sorted #define N 1000000 // A comparator function used by qsort int compare(const void * a const void * b) { return ( *(int*)a - *(int*)b ); } // Driver program to test above functions int main() { int arr[N] dupArr[N]; // seed for random input srand(time(NULL)); // to measure time taken by qsort and sort clock_t begin end; double time_spent; // generate random input for (int i = 0; i < N; i++) dupArr[i] = arr[i] = rand()%100000; begin = clock(); qsort(arr N sizeof(int) compare); end = clock(); // calculate time taken by C qsort function time_spent = (double)(end - begin) / CLOCKS_PER_SEC; cout << 'Time taken by C qsort() - ' << time_spent << endl; time_spent = 0.0; begin = clock(); sort(dupArr dupArr + N); end = clock(); // calculate time taken by C++ sort time_spent = (double)(end - begin) / CLOCKS_PER_SEC; cout << 'Time taken by C++ sort() - ' << time_spent << endl; return 0; }
Time taken by C qsort() - 0.247883 Time taken by C++ sort() - 0.086125
C++ sort() is blazingly faster than qsort() on equivalent data due to inlining. sort() on a container of integers will be compiled to use std::less::operator() by default which will be inlined and sort() will be comparing the integers directly. On the other hand qsort() will be making an indirect call through a function pointer for every comparison which compilers fails to optimize. 4. Fleksibilnost: STL -ova sorta djeluje za sve vrste podataka i za različite spremnike podataka poput C nizova C ++ vektora C ++ deques itd. I ostale spremnike koje korisnik može napisati. Ova vrsta fleksibilnosti prilično je teško postići u C. 5. Sigurnost: U usporedbi s QSORT-om, predložena sorta je sigurna jer ne zahtijeva pristup podatkovnim predmetima putem nesigurnih praznih pokazivača kao što to čini QSORT. REFERENCE: http://theory.stanford.edu/~amitp/rants/c++-vs-c/ https://en.wikipedia.org/wiki/sort_(c%2b%2b)
