Initial data commit

Task/Sorting-algorithms-Permutation-sort/C/sorting-algorithms-permutation-sort.c

@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef int(*cmp_func)(const void*, const void*);
+
+void perm_sort(void *a, int n, size_t msize, cmp_func _cmp)
+{
+	char *p, *q, *tmp = malloc(msize);
+#	define A(i) ((char *)a + msize * (i))
+#	define swap(a, b) {\
+		memcpy(tmp, a, msize);\
+		memcpy(a, b, msize);\
+		memcpy(b, tmp, msize);	}
+	while (1) {
+		/* find largest k such that a[k - 1] < a[k] */
+		for (p = A(n - 1); (void*)p > a; p = q)
+			if (_cmp(q = p - msize, p) > 0)
+				break;
+
+		if ((void*)p <= a) break;
+
+		/* find largest l such that a[l] > a[k - 1] */
+		for (p = A(n - 1); p > q; p-= msize)
+			if (_cmp(q, p) > 0) break;
+
+		swap(p, q); /* swap a[k - 1], a[l] */
+		/* flip a[k] through a[end] */
+		for (q += msize, p = A(n - 1); q < p; q += msize, p -= msize)
+			swap(p, q);
+	}
+	free(tmp);
+}
+
+int scmp(const void *a, const void *b) { return strcmp(*(const char *const *)a, *(const char *const *)b); }
+
+int main()
+{
+	int i;
+	const char *strs[] = { "spqr", "abc", "giant squid", "stuff", "def" };
+	perm_sort(strs, 5, sizeof(*strs), scmp);
+
+	for (i = 0; i < 5; i++)
+		printf("%s\n", strs[i]);
+	return 0;
+}