merge: add merge sort (#456)

* add merge sort * change code style * move iterative implementation to mergesort.go * fix: rename MegrgeSortIter to MergeIter Co-authored-by: zhaodeliang <[email protected]> Co-authored-by: Rak Laptudirm <[email protected]>
TheAlgorithms · Jan 4, 2022 · 6134d6e · 6134d6e
1 parent a918456
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diff --git a/sort/mergesort.go b/sort/mergesort.go
@@ -1,5 +1,7 @@
 package sort
 
+import "github.com/TheAlgorithms/Go/math/min"
+
 func merge(a []int, b []int) []int {
 
 	var r = make([]int, len(a)+len(b))
@@ -45,3 +47,13 @@ func Mergesort(items []int) []int {
 	return merge(a, b)
 
 }
+
+func MergeIter(items []int) []int {
+	for step := 1; step < len(items); step += step {
+		for i := 0; i+step < len(items); i += 2 * step {
+			tmp := merge(items[i:i+step], items[i+step:min.Int(i+2*step, len(items))])
+			copy(items[i:], tmp)
+		}
+	}
+	return items
+}
diff --git a/sort/sorts_test.go b/sort/sorts_test.go
@@ -90,6 +90,10 @@ func TestMerge(t *testing.T) {
 	testFramework(t, Mergesort)
 }
 
+func TestMergeIter(t *testing.T) {
+	testFramework(t, MergeIter)
+}
+
 func TestHeap(t *testing.T) {
 	testFramework(t, HeapSort)
 }
@@ -187,6 +191,10 @@ func BenchmarkMerge(b *testing.B) {
 	benchmarkFramework(b, Mergesort)
 }
 
+func BenchmarkMergeIter(b *testing.B) {
+	benchmarkFramework(b, MergeIter)
+}
+
 func BenchmarkHeap(b *testing.B) {
 	benchmarkFramework(b, HeapSort)
 }