[Bug Fix] of sorting/heapsort.cpp (#873)

* formatting source-code for 72c365dcd3

* Fixed Bug [munmap_chunck() core dumped]

* formatting source-code for b06bbf4dc6

* fixed line spacing

* fixed line spacing

* fixed documentation

* closed the paranthesis of line 3

* formatting source-code for 8233eda889

* Bug Fix heap sort [Fresh Implementation]

* formatting source-code for e464ddac36

* Bug Fix heap sort [Fresh Implementation]

* formatting source-code for 803981c831

* switched to normal functions from lambda

* formatting source-code for ced5dcd6c4

* Added template and test cases

* formatting source-code for 7c8617fa46

* fixed docs

* fixed line spacing in tests

* fix docs

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

sorting/heap_sort.cpp

@@ -1,52 +1,123 @@
+/**
+ * \file
+ * \brief [Heap Sort Algorithm
+ * (heap sort)](https://en.wikipedia.org/wiki/Heapsort) implementation
+ *
+ * \author [Ayaan Khan](http://github.com/ayaankhan98)
+ *
+ * \details
+ *  Heap-sort is a comparison-based sorting algorithm.
+ *  Heap-sort can be thought of as an improved selection sort:
+ *  like selection sort, heap sort divides its input into a sorted
+ *  and an unsorted region, and it iteratively shrinks the unsorted
+ *  region by extracting the largest element from it and inserting
+ *  it into the sorted region. Unlike selection sort,
+ *  heap sort does not waste time with a linear-time scan of the
+ *  unsorted region; rather, heap sort maintains the unsorted region
+ *  in a heap data structure to more quickly find the largest element
+ *  in each step.
+ *
+ *  Time Complexity - \f$O(n \log(n))\f$
+ *
+ */
 #include <algorithm>
+#include <cassert>
 #include <iostream>
 
-void heapify(int *a, int i, int n) {
+/**
-    int largest = i;
+ *
-    const int l = 2 * i + 1;
+ * Utility Lambda function to print the array after
-    const int r = 2 * i + 2;
+ * sorting.
+ *
+ * @param arr array to be printed
+ * @param sz size of array
+ *
+ */
+template <typename T>
+void printArray(T *arr, int sz) {
+    for (int i = 0; i < sz; i++) std::cout << arr[i] << "  ";
+    std::cout << "\n";
+}
 
-    if (l < n && a[l] > a[largest])
+/**
+ *
+ * \addtogroup sorting Sorting Algorithm
+ * @{
+ *
+ * The heapify procedure can be thought of as building a heap from
+ * the bottom up by successively sifting downward to establish the
+ * heap property.
+ *
+ * @param arr array to be sorted
+ * @param n size of array
+ * @param i node position in Binary Tress or element position in
+ *          Array to be compared with it's childern
+ *
+ */
+template <typename T>
+void heapify(T *arr, int n, int i) {
+    int largest = i;
+    int l = 2 * i + 1;
+    int r = 2 * i + 2;
+
+    if (l < n && arr[l] > arr[largest])
         largest = l;
 
-    if (r < n && a[r] > a[largest])
+    if (r < n && arr[r] > arr[largest])
         largest = r;
 
     if (largest != i) {
-        std::swap(a[i], a[largest]);
+        std::swap(arr[i], arr[largest]);
-        heapify(a, n, largest);
+        heapify(arr, n, largest);
     }
 }
 
-void heapsort(int *a, int n) {
+/**
-    for (int i = n - 1; i >= 0; --i) {
+ * Utilizes heapify procedure to sort
-        std::swap(a[0], a[i]);
+ * the array
-        heapify(a, 0, i);
+ *
+ * @param arr array to be sorted
+ * @param n size of array
+ *
+ */
+template <typename T>
+void heapSort(T *arr, int n) {
+    for (int i = n - 1; i >= 0; i--) heapify(arr, n, i);
+
+    for (int i = n - 1; i >= 0; i--) {
+        std::swap(arr[0], arr[i]);
+        heapify(arr, i, 0);
     }
 }
 
-void build_maxheap(int *a, int n) {
+/**
-    for (int i = n / 2 - 1; i >= 0; --i) {
+ *
-        heapify(a, i, n);
+ * @}
-    }
+ * Test cases to test the program
+ *
+ */
+void test() {
+    std::cout << "Test 1\n";
+    int arr[] = {-10, 78, -1, -6, 7, 4, 94, 5, 99, 0};
+    int sz = sizeof(arr) / sizeof(arr[0]);  // sz - size of array
+    printArray(arr, sz);  // displaying the array before sorting
+    heapSort(arr, sz);    // calling heapsort to sort the array
+    printArray(arr, sz);  // display array after sorting
+    assert(std::is_sorted(arr, arr + sz));
+    std::cout << "Test 1 Passed\n========================\n";
+
+    std::cout << "Test 2\n";
+    double arr2[] = {4.5, -3.6, 7.6, 0, 12.9};
+    sz = sizeof(arr2) / sizeof(arr2[0]);
+    printArray(arr2, sz);
+    heapSort(arr2, sz);
+    printArray(arr2, sz);
+    assert(std::is_sorted(arr2, arr2 + sz));
+    std::cout << "Test 2 passed\n";
 }
 
+/** Main function */
 int main() {
-    int n;
+    test();
-    std::cout << "Enter number of elements of array\n";
+    return 0;
-    std::cin >> n;
-    int a[20];
-    for (int i = 0; i < n; ++i) {
-        std::cout << "Enter Element " << i << std::endl;
-        std::cin >> a[i];
-    }
-
-    build_maxheap(a, n);
-    heapsort(a, n);
-    std::cout << "Sorted Output\n";
-    for (int i = 0; i < n; ++i) {
-        std::cout << a[i] << std::endl;
-    }
-
-    std::getchar();
 }