factorial

Signed-off-by: deemak <deema_k@mail.ru>

README.md

@@ -15,7 +15,8 @@
 
 ## Menu
 `Sorted`
-* [Sort-insertion](https://github.com/digital-technology-agency/math/wiki/Sort-insertion)
+* [Sort insertion](https://github.com/digital-technology-agency/math/wiki/Sort-insertion)
+* [Merge sort](https://github.com/digital-technology-agency/math/wiki/Merge-sort)
 
 `Mathematical`
 
@@ -24,6 +25,7 @@
 * [Permutation](https://github.com/digital-technology-agency/math/wiki/Permutation)
 * [Placements](https://github.com/digital-technology-agency/math/wiki/Placements)
 
+
 ## Examples
 
 ### C from n to k

pkg/sort/merge-sort.go

@@ -0,0 +1,30 @@
+package sort
+
+func Merge(input []int) []int {
+	length := len(input)
+	if length < 2 {
+		return input
+	}
+	mid := length / 2
+	return internalMerge(Merge(input[:mid]), Merge(input[mid:]))
+}
+
+func internalMerge(left, right []int) []int {
+	result := []int{}
+	for len(left) > 0 && len(right) > 0 {
+		if left[0] < right[0] {
+			result = append(result, left[0])
+			left = left[1:]
+		} else {
+			result = append(result, right[0])
+			right = right[1:]
+		}
+	}
+	if len(left) > 0 {
+		result = append(result, left...)
+	}
+	if len(right) > 0 {
+		result = append(result, right...)
+	}
+	return result
+}

pkg/sort/merge-sort_test.go

@@ -0,0 +1,35 @@
+package sort
+
+import (
+	"log"
+	"testing"
+)
+
+func TestMerge(t *testing.T) {
+	type args struct {
+		size int
+	}
+	tests := []struct {
+		name string
+		args args
+		want int
+	}{
+		{
+			name: "Merge sort",
+			args: args{
+				size: 100,
+			},
+			want: 0,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			inputArray := randomArray(tt.args.size)
+			got := Merge(inputArray)
+			log.Printf(`Result: %v`, got)
+			if got[0] < tt.want {
+				t.Errorf("Merge() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

pkg/sort/sort-by-insertion_test.go

@@ -2,6 +2,7 @@ package sort
 
 import (
 	"crypto/rand"
+	"log"
 	"math/big"
 	"testing"
 )
@@ -22,15 +23,17 @@ func TestInsertion(t *testing.T) {
 		{
 			name: "Sort by insertion",
 			args: args{
-				size: 10000,
+				size: 100,
 			},
-			want: 1,
+			want: 0,
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			inputArray := randomArray(tt.args.size)
-			if got := Insertion(inputArray); got[0] != tt.want && got[0] > tt.want {
+			got := Insertion(inputArray)
+			log.Printf(`Result: %v`, got)
+			if got[0] < tt.want {
 				t.Errorf("Insertion() = %v, want %v", got, tt.want)
 			}
 		})
@@ -42,7 +45,8 @@ func randomArray(size int) []int {
 	n, _ := rand.Int(rand.Reader, big.NewInt(int64(size)))
 	total := n.Int64()
 	for total > 0 {
-		result = append(result, int(total))
+		value, _ := rand.Int(rand.Reader, big.NewInt(int64(size)))
+		result = append(result, int(value.Int64()))
 		total--
 	}
 	return result