Merge pull request TheAlgorithms#53 from Triaro/patch-3

heap_sort.m

algorithms/sorting/heap_sort.m

@@ -0,0 +1,40 @@
+function list = heapSort(list)
+
+    function list = siftDown(list,root,theEnd) 
+        while (root * 2) <= theEnd
+
+            child = root * 2;
+            if (child + 1 <= theEnd) && (list(child) < list(child+1))
+                child = child + 1;
+            end
+
+            if list(root) < list(child)
+                list([root child]) = list([child root]); %Swap
+                root = child;
+            else
+                return
+            end
+
+        end %while
+    end %siftDown
+
+    count = numel(list);
+
+    %Because heapify is called once in pseudo-code, it is inline here
+    start = floor(count/2);
+
+    while start >= 1
+        list = siftDown(list, start, count);
+        start = start - 1;
+    end
+    %End Heapify
+
+    while count > 1
+
+        list([count 1]) = list([1 count]); %Swap        
+        count = count - 1;
+        list = siftDown(list,1,count);
+
+    end
+
+end