From da2dd3643933b3c05b60344de376b4dd8d59580b Mon Sep 17 00:00:00 2001
From: Giovanny Massuia <giovannycmassuia@gmail.com>
Date: Sun, 7 Jul 2024 08:22:58 -0700
Subject: [PATCH] merge sort

---
 go-dsa/sorting/merge_sort.go   | 64 ++++++++++++++++++++++++++++++++++
 go-dsa/sorting/sorting_test.go |  1 +
 2 files changed, 65 insertions(+)
 create mode 100644 go-dsa/sorting/merge_sort.go

diff --git a/go-dsa/sorting/merge_sort.go b/go-dsa/sorting/merge_sort.go
new file mode 100644
index 0000000..b6dba57
--- /dev/null
+++ b/go-dsa/sorting/merge_sort.go
@@ -0,0 +1,64 @@
+package sorting
+
+type MergeSort struct{}
+
+func (i *MergeSort) Sort(arr []int) {
+	// Divide: Divide the list or array recursively into two halves until it can no more be divided.
+	// Conquer: Each subarray is sorted individually using the merge sort algorithm.
+	// Merge: The sorted subarrays are merged back together in sorted order.
+	//		  The process continues until all elements from both subarrays have been merged.
+	mergeSort(arr, 0, len(arr)-1)
+}
+
+func mergeSort(arr []int, l, r int) {
+	if l < r {
+		m := l + (r-l)/2
+		mergeSort(arr, l, m)
+		mergeSort(arr, m+1, r)
+		merge(arr, l, m, r)
+	}
+}
+
+func merge(arr []int, l, m, r int) {
+	n1 := m - l + 1
+	n2 := r - m
+
+	// Create temporary arrays
+	L := make([]int, n1)
+	R := make([]int, n2)
+
+	// Copy data to temporary arrays
+	for i := 0; i < n1; i++ {
+		L[i] = arr[l+i]
+	}
+	for i := 0; i < n2; i++ {
+		R[i] = arr[m+1+i]
+	}
+
+	// Merge the temporary arrays back into arr[l..r]
+	i, j, k := 0, 0, l
+	for i < n1 && j < n2 {
+		if L[i] <= R[j] {
+			arr[k] = L[i]
+			i++
+		} else {
+			arr[k] = R[j]
+			j++
+		}
+		k++
+	}
+
+	// Copy the remaining elements of L[] if there are any
+	for i < n1 {
+		arr[k] = L[i]
+		i++
+		k++
+	}
+
+	// Copy the remaining elements of R[] if there are any
+	for j < n2 {
+		arr[k] = R[j]
+		j++
+		k++
+	}
+}
diff --git a/go-dsa/sorting/sorting_test.go b/go-dsa/sorting/sorting_test.go
index 851a49d..f2259da 100644
--- a/go-dsa/sorting/sorting_test.go
+++ b/go-dsa/sorting/sorting_test.go
@@ -16,6 +16,7 @@ func TestSorting(t *testing.T) {
 		&InsertionSort{},
 		&HeapSort{},
 		&ShellSort{},
+		&MergeSort{},
 	}
 
 	tests := buildTestData()