Merge pull request xtaci#43 from yanzhe-chen/heap-bug-fix

Fix two bugs in heap implementation.

Author: xtaci

Makefile

@@ -13,6 +13,7 @@ LIBS = -lm
 PROGRAMS = m_based_demo \
 			integer_demo \
        		insertion_sort_demo \
+					shell_sort_demo \
        		radix_sort_demo \
        		shuffle_demo \
            	quick_sort_demo \
@@ -81,6 +82,9 @@ integer_demo: $(SRCDIR)/integer_demo.cpp
 insertion_sort_demo: $(SRCDIR)/insertion_sort_demo.cpp
 	$(CPP) $(CFLAGS) -o $@ $^ $(INCLUDEDIR) $(LIBS)
 
+shell_sort_demo: $(SRCDIR)/shell_sort_demo.cpp
+	$(CPP) $(CFLAGS) -o $@ $^ $(INCLUDEDIR) $(LIBS)
+
 radix_sort_demo: $(SRCDIR)/radix_sort_demo.cpp
 	$(CPP) $(CFLAGS) -o $@ $^ $(INCLUDEDIR) $(LIBS)
 

README.md

@@ -41,6 +41,7 @@
     Bubble sort
     Selection sort
     Insertion sort
+    Shell sort
     Radix sort
     Quick sort
     Merge sort

include/heap.h

@@ -61,7 +61,7 @@ namespace alg {
 			public:
 				Heap(int max) {
 					m_size = 0;
-					m_max = max+1;
+					m_max = max;
 					m_heap = new elem[m_max];
 				};
 
@@ -101,7 +101,7 @@ namespace alg {
 				inline void clear() { m_size = 0; }
 
 				bool contains(const T & data) {
-					for(int i=1;i<=m_size;i++) {
+					for(int i=0;i<m_size;i++) {
 						if(m_heap[i].data== data) return true;
 					}
 					return false;
@@ -166,7 +166,7 @@ namespace alg {
 						}
 
 						int j = j1;
-						int j2 = j1+1; // left child
+						int j2 = j1+1; // right child
 						if (j2 < n && !less(j1,j2)) {
 							j = j2; 	// choose the minium one.
 						}

include/shell_sort.h

@@ -0,0 +1,44 @@
+/*******************************************************************************
+ * DANIEL'S ALGORITHM IMPLEMENTAIONS
+ *
+ *  /\  |  _   _  ._ o _|_ |_  ._ _   _ 
+ * /--\ | (_| (_) |  |  |_ | | | | | _> 
+ *         _|                      
+ * 
+ * SHELL SORT 
+ *
+ * 1. sort array in O(n^(3/2)) time.
+ * 
+ * https://en.wikipedia.org/wiki/Shellsort
+ *
+ ******************************************************************************/
+
+#ifndef __SHELL_SORT_H__
+#define __SHELL_SORT_H__
+
+namespace alg {
+	/**
+	 * shell sort an array
+	 */
+	template<typename T>
+		static void shell_sort(T *array, int len) {
+      int h = 1;
+      while (h < len / 3) {
+        h = 3 * h + 1; // 1, 4, 13, 40, 121, ...
+      }
+      while (h >= 1) {
+        for (int i = h; i < len; i++) {
+          int cur = array[i];
+          int j = i - h;
+          while (j >= 0 && array[j] > cur) {
+            array[j + h] = array[j];
+            j = j - h;
+          }
+          array[j + h] = cur;
+        }
+        h = h / 3;
+      }
+		}
+}
+
+#endif //

src/shell_sort_demo.cpp

@@ -0,0 +1,32 @@
+#include <stdio.h>  
+#include <stdlib.h>  
+#include <time.h>
+
+#include "generic.h"
+#include "shell_sort.h"
+
+using namespace alg;
+
+int main()
+{
+	const int MAX_ELEMENTS = 10;
+	int list[MAX_ELEMENTS];
+
+	int i = 0;
+
+	srand(time(NULL));
+	// generate random numbers and fill them to the list
+	for(i = 0; i < MAX_ELEMENTS; i++ ){
+		list[i] = rand()%100;
+	}
+	printf("The list before sorting is:\n");
+	printlist(list,MAX_ELEMENTS);
+
+	// sort the list using shell sort
+	shell_sort<int>(&list[0],MAX_ELEMENTS);  
+
+	// print the result
+	printf("The list after sorting using shell sort algorithm:\n");
+	printlist(list,MAX_ELEMENTS);
+	return 0;
+}