added merge-sort.go

merge-sort/merge-sort.go

@@ -0,0 +1,92 @@
+// ====================================================
+// Data-Structures-with-Go Copyright(C) 2017 Furkan Türkal
+// This program comes with ABSOLUTELY NO WARRANTY; This is free software,
+// and you are welcome to redistribute it under certain conditions; See
+// file LICENSE, which is part of this source code package, for details.
+// ====================================================
+
+package main
+
+import "fmt"
+
+func Merge(arr []int, l, m, r int){
+	var i, j, k int
+	var n1 int = m - l + 1
+	var n2 int = r - m
+
+	//Create temp arrays
+	L := make([]int, n1)
+	R := make([]int, n2)
+
+	//Copy data to temp arrays L[] and R[]
+	for i = 0; i < n1; i++ {
+		L[i] = arr[l + i]
+	}
+
+	for j = 0; j < n2; j++ {
+		R[j] = arr[m + 1 + j]
+	}
+
+	//Merge the temp arrays back into arr[l..r]
+	i = 0 //Initial index of first subarray
+	j = 0 //Initial index of second subarray
+	k = l //Initial index of merged subarray
+
+	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++
+	}
+}
+
+func MergeSort(arr []int, l, r int){
+	if(l < r){
+		//Same as (l + r) / 2 but avoids overflow for large l and h
+		var m int = l + (r - l) / 2
+
+		//Sort first and second halves
+		MergeSort(arr, l, m)
+		MergeSort(arr, m + 1, r)
+
+		Merge(arr, l, m, r)
+	}
+}
+
+func PrintArray(A []int, size int){
+	for i:=0; i < size; i++ {
+		fmt.Printf("%d ", A[i])
+	}
+	fmt.Printf("\n")
+}
+
+func main() {
+	arr := []int{12, 11, 13, 5, 6, 7}
+	var arr_size int = len(arr)
+
+	fmt.Println("Given array size is: ")
+	PrintArray(arr, arr_size)
+
+	MergeSort(arr, 0, arr_size - 1)
+
+	fmt.Println("Sorted array is: ")
+	PrintArray(arr, arr_size)
+}