contains-duplicate: refactor function

Author: Invidam

contains-duplicate/invidam.go

@@ -1,12 +1,9 @@
 func containsDuplicate(nums []int) bool {
-	appeared := make(map[int]bool, len(nums)/4)
+	appeared := make(map[int]bool)
 
 	for _, num := range nums {
-		if _, found := appeared[num]; found {
-			return true
-		}
 		appeared[num] = true
 	}
 
-	return false
-}
+	return len(appeared) != len(nums)
+}