From 50873ce45028eb266bef5d5e21ed8f0429a69d14 Mon Sep 17 00:00:00 2001
From: david <david@pinewoods.xyz>
Date: Wed, 8 Oct 2025 12:12:00 -0500
Subject: [PATCH] Add initial cpp heapsort, needs refactor (likely use
 constexpr)

---
 cpp/algorithms/sort_heap.cpp |  2 +
 cpp/algorithms/sort_heap.hpp | 23 ++++++++++
 cpp/data_structures/heap.cpp |  2 +
 cpp/data_structures/heap.hpp | 82 ++++++++++++++++++++++++++++++++++++
 cpp/test.cpp                 | 29 +++++++++++++
 5 files changed, 138 insertions(+)
 create mode 100644 cpp/algorithms/sort_heap.cpp
 create mode 100644 cpp/algorithms/sort_heap.hpp
 create mode 100644 cpp/data_structures/heap.cpp
 create mode 100644 cpp/data_structures/heap.hpp
 create mode 100644 cpp/test.cpp

diff --git a/cpp/algorithms/sort_heap.cpp b/cpp/algorithms/sort_heap.cpp
new file mode 100644
index 0000000..ce1aa67
--- /dev/null
+++ b/cpp/algorithms/sort_heap.cpp
@@ -0,0 +1,2 @@
+namespace dlos {
+}
diff --git a/cpp/algorithms/sort_heap.hpp b/cpp/algorithms/sort_heap.hpp
new file mode 100644
index 0000000..7ec70b2
--- /dev/null
+++ b/cpp/algorithms/sort_heap.hpp
@@ -0,0 +1,23 @@
+#pragma once
+
+#include "../data_structures/heap.hpp"
+
+namespace dlos {
+
+    template<typename T, size_t N>
+    void heapsort(std::array<T, N> &a) {
+        dlos::Heap<T, N> heap = dlos::Heap<T, N>(a);
+        heap.maxHeap();
+        heapsort(heap);
+    }
+
+    template<typename T, size_t N>
+    void heapsort(Heap<T, N> &heap) {
+        for (int i = heap.size - 1; i > 0; i--) {
+            heap.nodeSwap(0, i);
+            heap.size -= 1;
+            heap.siftDown(0);
+        }
+    }
+
+}
diff --git a/cpp/data_structures/heap.cpp b/cpp/data_structures/heap.cpp
new file mode 100644
index 0000000..ce1aa67
--- /dev/null
+++ b/cpp/data_structures/heap.cpp
@@ -0,0 +1,2 @@
+namespace dlos {
+}
diff --git a/cpp/data_structures/heap.hpp b/cpp/data_structures/heap.hpp
new file mode 100644
index 0000000..b1e1d5a
--- /dev/null
+++ b/cpp/data_structures/heap.hpp
@@ -0,0 +1,82 @@
+#pragma once
+
+#include <array>
+
+// examples of how the heap can be used
+//
+// std::array<int, 10> a1 = {73, 6, 57, 88, 60, 42, 83, 72, 48, 85};
+// dlos::Heap<int, a1.size()> h = dlos::Heap<int, a1.size()>(a1);
+// h.maxHeap();
+// dlos::heapsort(h);
+// for (int i = 0; i < a1.size(); i++) {
+//     std::cout << h.getValueAt(i) << ", ";
+//     if (i == a1.size() - 1) std::cout << std::endl;
+// }
+//
+// std::array<int, 20> a2 = {98, 8, 108, 91, 139, 49, 181, 212, 77, 85, 73, 6, 57, 88, 60, 42, 83, 72, 48, 85};
+// dlos::heapsort(a2);
+// for (int i = 0; i < a2.size(); i++) {
+//     std::cout << a2[i] << ", ";
+//     if (i == a2.size() - 1) std::cout << std::endl;
+// }
+
+namespace dlos {
+
+    template <typename T, size_t N>
+    class Heap {
+        public:
+            int size = 0;
+
+        private:
+            std::array<T, N> &arr;
+
+        public:
+            Heap(std::array<T, N> &arr) : arr(arr) { size = N; }
+
+            T getValueAt(int i) const { return arr[i]; }
+
+            void nodeSwap(int a, int b) {
+                T temp = arr[a];
+                arr[a] = arr[b];
+                arr[b] = temp;
+            }
+
+            void siftDown(int i) {
+                int target = indexOfLargerChild(i);
+                while (target > 0 && arr[i] < arr[target]) {
+                    nodeSwap(i, target);
+                    i = target;
+                    target = indexOfLargerChild(i);
+                };
+            }
+
+            void maxHeap() {
+                for (int i = parent(size - 1); i >= 0; i--) {
+                    siftDown(i);
+                }
+            }
+
+        private:
+            int parent(int i) { return (i > 0) ? (i - 1) / 2 : -1; }
+
+            int leftChild(int i) { return i * 2 + 1; }
+
+            int rightChild(int i) { return i * 2 + 2; }
+
+            int leftSibling(int i) { return (i % 2 == 0) ? i - 1 : -1; }
+
+            int rightSibling(int i) { return (i % 2 == 1) ? i + 1 : -1; }
+
+            int indexOfLargerChild(int i) {
+                int larger = leftChild(i);
+                if (larger >= size) {
+                    return -1;
+                }
+                if (larger + 1 < size && arr[larger] < arr[larger + 1]) {
+                    larger = larger + 1;
+                }
+                return larger;
+            }
+    };
+
+}
diff --git a/cpp/test.cpp b/cpp/test.cpp
new file mode 100644
index 0000000..727bd99
--- /dev/null
+++ b/cpp/test.cpp
@@ -0,0 +1,29 @@
+#include <array>
+#include <iostream>
+
+#include "data_structures/heap.hpp"
+#include "algorithms/sort_heap.hpp"
+
+int main() {
+    std::array<int, 10> a1 = {73, 6, 57, 88, 60, 42, 83, 72, 48, 85};
+    dlos::Heap<int, a1.size()> h = dlos::Heap<int, a1.size()>(a1);
+    h.maxHeap();
+    dlos::heapsort(h);
+
+    for (int i = 0; i < a1.size(); i++) {
+        if (i == 0) std::cout << "sorted: ";
+        std::cout << h.getValueAt(i) << ", ";
+        if (i == a1.size() - 1) std::cout << std::endl;
+    }
+
+    std::array<int, 20> a2 = {98, 8, 108, 91, 139, 49, 181, 212, 77, 85, 73, 6, 57, 88, 60, 42, 83, 72, 48, 85};
+    dlos::heapsort(a2);
+
+    for (int i = 0; i < a2.size(); i++) {
+        if (i == 0) std::cout << "sorted: ";
+        std::cout << a2[i] << ", ";
+        if (i == a2.size() - 1) std::cout << std::endl;
+    }
+
+    return 0;
+}