Puzzle 16: Extract function to reverse a series of elements

1 files changed, 15 insertions, 3 deletions

diff --git a/16.c b/16.c
index 2954ef9..15e9671 100644
--- a/16.c
+++ b/16.c
@@ -26,11 +26,24 @@ qswap(void * base, size_t size, int i, int j)
 }
 
 
+void
+qreverse(void * base, size_t nmemb, size_t size)
+{
+	size_t i, j;
+
+	if (nmemb < 2)
+		return;
+
+	for (i = 0, j = nmemb - 1; i < j; ++i, --j)
+		qswap(base, size, i, j);
+}
+
+
 int
 qpermute(void * base, size_t nmemb, size_t size,
 		int(*compar)(const void *, const void *))
 {
-	size_t pivot, next = 0, i, j;
+	size_t pivot, next = 0, i;
 
 	if (nmemb < 2)
 		// No other permutations!
@@ -64,8 +77,7 @@ qpermute(void * base, size_t nmemb, size_t size,
 	qswap(base, size, pivot, next);
 
 	// Reverse all the elements after the new pivot
-	for (i = pivot + 1, j = nmemb - 1; i < j; ++i, --j)
-		qswap(base, size, i, j);
+	qreverse(base + (pivot + 1) * size, nmemb - (pivot + 1), size);
 
 	return 1;
 }