March 2014 update

Task/Sorting-algorithms-Quicksort/Objective-C/sorting-algorithms-quicksort.m

@@ -0,0 +1,34 @@
+void quicksortInPlace(NSMutableArray *array, NSInteger first, NSInteger last, NSComparator comparator) {
+    if (first >= last) return;
+    id pivot = array[(first + last) / 2];
+    NSInteger left = first;
+    NSInteger right = last;
+    while (left <= right) {
+        while (comparator(array[left], pivot) == NSOrderedAscending)
+            left++;
+        while (comparator(array[right], pivot) == NSOrderedDescending)
+            right--;
+        if (left <= right)
+            [array exchangeObjectAtIndex:left++ withObjectAtIndex:right--];
+    }
+    quicksortInPlace(array, first, right, comparator);
+    quicksortInPlace(array, left, last, comparator);
+}
+
+NSArray* quicksort(NSArray *unsorted, NSComparator comparator) {
+    NSMutableArray *a = [NSMutableArray arrayWithArray:unsorted];
+    quicksortInPlace(a, 0, a.count - 1, comparator);
+    return a;
+}
+
+int main(int argc, const char * argv[]) {
+    @autoreleasepool {
+        NSArray *a = @[ @1, @3, @5, @7, @9, @8, @6, @4, @2 ];
+        NSLog(@"Unsorted: %@", a);
+        NSLog(@"Sorted: %@", quicksort(a, ^(id x, id y) { return [x compare:y]; }));
+        NSArray *b = @[ @"Emil", @"Peg", @"Helen", @"Juergen", @"David", @"Rick", @"Barb", @"Mike", @"Tom" ];
+        NSLog(@"Unsorted: %@", b);
+        NSLog(@"Sorted: %@", quicksort(b, ^(id x, id y) { return [x compare:y]; }));
+    }
+    return 0;
+}