Adding merge sort

Author: bhavnavarshney

Go/sorting/mergesort.go

@@ -0,0 +1,45 @@
+package sorting
+
+func merge(arr []int, start, mid, end int) {
+	ln, rn := mid-start+1, end-mid
+	left := make([]int, ln)
+	for i := 0; i < ln; i++ {
+		left[i] = arr[start+i]
+	}
+	right := make([]int, rn)
+	for i := 0; i < rn; i++ {
+		right[i] = arr[mid+1+i]
+	}
+	list1Start, list2Start, k := 0, 0, start
+
+	for list1Start < ln && list2Start < rn {
+		if left[list1Start] <= right[list2Start] {
+			arr[k] = left[list1Start]
+			list1Start++
+		} else {
+			arr[k] = right[list2Start]
+			list2Start++
+		}
+		k++
+	}
+
+	for list1Start < ln {
+		arr[k] = left[list1Start]
+		list1Start++
+		k++
+	}
+
+	for list2Start < rn {
+		arr[k] = right[list2Start]
+		list2Start++
+		k++
+	}
+}
+func mergeSort(arr []int, start, end int) {
+	if start < end {
+		mid := (start + end) / 2
+		mergeSort(arr, start, mid)
+		mergeSort(arr, mid+1, end)
+		merge(arr, start, mid, end)
+	}
+}