Adding HeapSort

Author: bhavnavarshney

Go/sorting/heapsort.go

@@ -0,0 +1,46 @@
+/*
+	Parent : (i-1)/2
+	Left Child: (2*parent)+1
+	Right Child: (2*parent)+2
+
+	Note: The below code sorts the array in ascending order using max-heap! For descending, min-heap should be used
+*/
+
+package sorting
+
+import "fmt"
+
+func HeapSort(arr []int) {
+	n := len(arr)
+	fmt.Println(arr)
+	// Phase 1 : Building!
+	//Starts from the mid because if 1 side is sorted - the order will automatically get sorted!
+	for parent := n / 2; parent >= 0; parent-- {
+		buildHeap(arr, n, parent)
+	}
+
+	// Phase 2: Extraction
+	for i := n - 1; i >= 1; i-- {
+		arr[0], arr[i] = arr[i], arr[0]
+		buildHeap(arr, i, 0)
+	}
+}
+
+func buildHeap(arr []int, n, parent int) {
+	largestElementIndex := parent
+	leftChild := parent*2 + 1
+	rightChild := parent*2 + 2
+
+	if leftChild < n && arr[leftChild] > arr[largestElementIndex] {
+		largestElementIndex = leftChild
+	}
+	if rightChild < n && arr[rightChild] > arr[largestElementIndex] {
+		largestElementIndex = rightChild
+	}
+
+	if largestElementIndex != parent {
+		arr[largestElementIndex], arr[parent] = arr[parent], arr[largestElementIndex]
+		buildHeap(arr, n, largestElementIndex)
+	}
+
+}

Go/sorting/heapsort_test.go

@@ -0,0 +1,48 @@
+/*
+	Parent : (i-1)/2
+	Left Child: (2*parent)+1
+	Right Child: (2*parent)+2
+
+	Note: The below code sorts the array in ascending order using max-heap! For descending, min-heap should be used
+*/
+
+package sorting
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestHeapSort(t *testing.T) {
+	type args struct {
+		arr []int
+	}
+	tests := []struct {
+		name   string
+		args   args
+		passed []int
+	}{
+		{
+			name: "test-01",
+			args: args{
+				arr: []int{3, 14, 10, 12, 24, 6, 2, 17},
+			},
+			passed: []int{2, 3, 6, 10, 12, 14, 17, 24},
+		},
+		{
+			name: "test-02",
+			args: args{
+				arr: []int{10, 2, 1, 3, 12, 8, 20},
+			},
+			passed: []int{1, 2, 3, 8, 10, 12, 20},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			HeapSort(tt.args.arr)
+			if !reflect.DeepEqual(tt.args.arr, tt.passed) {
+				t.Errorf("Got:%v but want:%v", tt.args.arr, tt.passed)
+			}
+		})
+	}
+}