Use getchar over getch (#681)

* Use getchar over getch

getch in Windows specific. Now the code will compile
and work on other platforms like Linux and macOS.

* Update and rename Heap Sort .cpp to heap_sort .cpp

* cpplint fixes

* Rename heap_sort .cpp to heap_sort.cpp

sorting/heap_sort.cpp

@@ -0,0 +1,51 @@
+#include <iostream>
+
+void max_heapify(int *a, int i, int n) {
+    int j, temp;
+    temp = a[i];
+    j = 2 * i;
+    while (j <= n) {
+        if (j < n && a[j + 1] > a[j])
+            j = j + 1;
+        if (temp > a[j]) {
+            break;
+        } else if (temp <= a[j]) {
+            a[j / 2] = a[j];
+            j = 2 * j;
+        }
+    }
+    a[j / 2] = temp;
+    return;
+}
+void heapsort(int *a, int n) {
+    int i, temp;
+    for (i = n; i >= 2; i--) {
+        temp = a[i];
+        a[i] = a[1];
+        a[1] = temp;
+        max_heapify(a, 1, i - 1);
+    }
+}
+void build_maxheap(int *a, int n) {
+    int i;
+    for (i = n / 2; i >= 1; i--) {
+        max_heapify(a, i, n);
+    }
+}
+int main() {
+    int n, i, x;
+    std::cout << "Enter number of elements of array\n";
+    std::cin >> n;
+    int a[20];
+    for (i = 1; i <= n; i++) {
+        std::cout << "Enter Element " << (i) << endl;
+        std::cin >> a[i];
+    }
+    build_maxheap(a, n);
+    heapsort(a, n);
+    std::cout << "Sorted Output\n";
+    for (i = 1; i <= n; i++) {
+        std::cout << a[i] << endl;
+    }
+    std::getchar();
+}