From 15a7d839e23304be7790dc85925752db5d04ce13 Mon Sep 17 00:00:00 2001
From: Giovanny Massuia <giovannycmassuia@gmail.com>
Date: Fri, 28 Jun 2024 07:26:15 -0700
Subject: [PATCH] heap sort

---
 go-dsa/sorting/heap_sort.go      | 39 +++++++++++++++++++++++++++++
 go-dsa/sorting/heap_sort_test.go | 42 ++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 go-dsa/sorting/heap_sort.go
 create mode 100644 go-dsa/sorting/heap_sort_test.go

diff --git a/go-dsa/sorting/heap_sort.go b/go-dsa/sorting/heap_sort.go
new file mode 100644
index 0000000..146ec7b
--- /dev/null
+++ b/go-dsa/sorting/heap_sort.go
@@ -0,0 +1,39 @@
+package sorting
+
+type HeapSort struct{}
+
+func (h *HeapSort) Sort(arr []int) {
+	h.heapifyArray(arr)
+
+	for i := len(arr) - 1; i >= 0; i-- {
+		arr[0], arr[i] = arr[i], arr[0]
+		h.heapify(arr, 0, i)
+	}
+}
+
+// heapifyArray the array as a max heap
+func (h *HeapSort) heapifyArray(arr []int) {
+	for i := len(arr) / 2; i >= 0; i-- {
+		h.heapify(arr, i, len(arr))
+	}
+}
+
+// heapify
+func (h *HeapSort) heapify(arr []int, i int, n int) {
+	ref := i
+	left := 2*i + 1
+	right := 2*i + 2
+
+	if left < n && arr[left] > arr[ref] {
+		ref = left
+	}
+
+	if right < n && arr[right] > arr[ref] {
+		ref = right
+	}
+
+	if ref != i {
+		arr[i], arr[ref] = arr[ref], arr[i]
+		h.heapify(arr, ref, n)
+	}
+}
diff --git a/go-dsa/sorting/heap_sort_test.go b/go-dsa/sorting/heap_sort_test.go
new file mode 100644
index 0000000..bdb21fb
--- /dev/null
+++ b/go-dsa/sorting/heap_sort_test.go
@@ -0,0 +1,42 @@
+package sorting
+
+import (
+	"testing"
+)
+
+func TestHeapSort(t *testing.T) {
+
+	tests := []struct {
+		input    []int
+		expected []int
+	}{
+		{[]int{10, 20, 15, 40, 50, 100, 25, 45}, []int{10, 15, 20, 25, 40, 45, 50, 100}},
+		{[]int{10, 9, 8, 7, 6, 5, 4, 3, 2, 1}, []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}},
+		{[]int{10, 20, 15, 40, 50, 100, 25, 45, 5, 35}, []int{5, 10, 15, 20, 25, 35, 40, 45, 50, 100}},
+	}
+
+	heapSort := HeapSort{}
+	for _, test := range tests {
+		// given
+		actual := make([]int, len(test.input))
+		copy(actual, test.input)
+
+		// when
+		heapSort.Sort(actual)
+
+		// then
+		if !compareArray(actual, test.expected) {
+			t.Errorf("Test failed! Expected = %v, Actual = %v", test.expected, actual)
+		}
+	}
+}
+
+func compareArray(actual, expected []int) bool {
+	for i := 0; i < len(expected); i++ {
+		if actual[i] != expected[i] {
+			return false
+		}
+	}
+
+	return true
+}