Sorting algorithms/Cocktail sort: Difference between revisions

===Generic version===

This version can be used with arrays of any type, like the standard library function qsort.

<lang c>#include <stdbool.h>

#include <stdio.h>

#include <string.h>

void swap(char* p1, char* p2, size_t size) {

for (; size-- > 0; ++p1, ++p2) {

char tmp = *p1;

*p1 = *p2;

*p2 = tmp;

}

}

void cocktail_sort(void* base, size_t count, size_t size,

int (*cmp)(const void*, const void*)) {

char* begin = base;

char* end = base + size * count;

if (end == begin)

return;

for (end -= size; ; ) {

bool swapped = false;

for (char* p = begin; p < end; p += size) {

char* q = p + size;

if (cmp(p, q) > 0) {

swap(p, q, size);

swapped = true;

}

}

if (swapped) {

for (char* p = end; p > begin; p -= size) {

char* q = p - size;

if (cmp(q, p) > 0) {

swap(p, q, size);

swapped = true;

}

}

}

if (!swapped)

break;

}

}

int string_compare(const void* p1, const void* p2) {

const char* const* s1 = p1;

const char* const* s2 = p2;

return strcmp(*s1, *s2);

}

void print(const char** a, size_t len) {

for (size_t i = 0; i < len; ++i)

printf("%s ", a[i]);

printf("\n");

}

int main() {

const char* a[] = { "one", "two", "three", "four", "five",

"six", "seven", "eight", "nine", "ten" };

const size_t len = sizeof(a)/sizeof(a[0]);

printf("before: ");

print(a, len);

cocktail_sort(a, len, sizeof(char*), string_compare);

printf("after: ");

print(a, len);

return 0;

}</lang>

{{out}}

<pre>

before: one two three four five six seven eight nine ten

after: eight five four nine one seven six ten three two

</pre>