len calculation

diffmatchpatch/diff.go

diff --git a/diffmatchpatch/diff.go b/diffmatchpatch/diff.go
index b03f7e3..a7dfa08 100644
--- a/diffmatchpatch/diff.go
+++ b/diffmatchpatch/diff.go
@@ -728,8 +728,8 @@
 			overlapLength1 := dmp.DiffCommonOverlap(deletion, insertion)
 			overlapLength2 := dmp.DiffCommonOverlap(insertion, deletion)
 			if overlapLength1 >= overlapLength2 {
-				if float64(overlapLength1) >= float64(len(deletion))/2 ||
-					float64(overlapLength1) >= float64(len(insertion))/2 {
+				if float64(overlapLength1) >= float64(len([]rune(deletion)))/2 ||
+					float64(overlapLength1) >= float64(len([]rune(insertion)))/2 {
 
 					// Overlap found. Insert an equality and trim the surrounding edits.
 					diffs = splice(diffs, pointer, 0, Diff{DiffEqual, insertion[:overlapLength1]})