Merge pull request #393 from openset/develop

Update: Merge Two Sorted Lists

Author: Shuo

problems/merge-two-sorted-lists/merge_two_sorted_lists.go

@@ -10,22 +10,14 @@ import . "github.com/openset/leetcode/internal/kit"
  * }
  */
 func mergeTwoLists(l1 *ListNode, l2 *ListNode) *ListNode {
-	l := &ListNode{}
-	t := l
-	for l1 != nil && l2 != nil {
-		if l1.Val < l2.Val {
-			t.Next = l1
-			l1 = l1.Next
-		} else {
-			t.Next = l2
-			l2 = l2.Next
-		}
-		t = t.Next
-	}
 	if l1 == nil {
-		t.Next = l2
-	} else {
-		t.Next = l1
+		return l2
+	} else if l2 == nil {
+		return l1
+	}
+	if l1.Val > l2.Val {
+		l1, l2 = l2, l1
 	}
-	return l.Next
+	l1.Next = mergeTwoLists(l1.Next, l2)
+	return l1
 }

problems/merge-two-sorted-lists/merge_two_sorted_lists_test.go

@@ -32,8 +32,13 @@ func TestMergeTwoLists(t *testing.T) {
 		},
 		{
 			l1:       []int{1, 2, 3},
-			l2:       []int{1, 2, 3},
-			expected: []int{1, 1, 2, 2, 3, 3},
+			l2:       nil,
+			expected: []int{1, 2, 3},
+		},
+		{
+			l1:       []int{1, 2, 3, 8, 16},
+			l2:       []int{1, 2, 3, 10, 12, 24},
+			expected: []int{1, 1, 2, 2, 3, 3, 8, 10, 12, 16, 24},
 		},
 	}
 	for _, tc := range tests {