Merge https://github.com/yanglbme/leetcode

Author: chakyam

README.md

@@ -13,6 +13,7 @@ Complete solutions to Leetcode problems, updated daily.
 | # | Title | Tags |
 |---|---|---|
 | 001 | [Two Sum](https://github.com/yanglbme/leetcode/tree/master/solution/001.Two%20Sum) | `Array`, `Hash Table` |
+| 021 | [Merge Two Sorted Lists](https://github.com/yanglbme/leetcode/tree/master/solution/021.Merge%20Two%20Sorted%20Lists) | `Linked List` |
 | 203 | [Remove Linked List Elements](https://github.com/yanglbme/leetcode/tree/master/solution/203.Remove%20Linked%20List%20Elements) | `Linked List` |
 
 ### Medium
@@ -33,7 +34,7 @@ I'm looking for long-term contributors/partners to this repo! Send me PRs if you
 ## Contributors
 
 <!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
-| <center> [<img src="https://avatars3.githubusercontent.com/u/21008209?v=4" width="100px;"/><br /><sub><b>yanglbme</b></sub>](https://github.com/yanglbme)<br />[💻](https://github.com/yanglbme/leetcode/commits?author=yanglbme "Code") </center> | <center> [<img src="https://avatars3.githubusercontent.com/u/21008209?v=4" width="100px;"/><br /><sub><b>yanglbme</b></sub>](https://github.com/yanglbme)<br />[💻](https://github.com/yanglbme/leetcode/commits?author=yanglbme "Code") </center> | <center>[<img src="https://avatars3.githubusercontent.com/u/21008209?v=4" width="100px;"/><br /><sub><b>yanglbme</b></sub>](https://github.com/yanglbme)<br />[💻](https://github.com/yanglbme/leetcode/commits?author=yanglbme "Code") </center> | <center> [<img src="https://avatars3.githubusercontent.com/u/21008209?v=4" width="100px;"/><br /><sub><b>yanglbme</b></sub>](https://github.com/yanglbme)<br />[💻](https://github.com/yanglbme/leetcode/commits?author=yanglbme "Code") </center> | <center> [<img src="https://avatars3.githubusercontent.com/u/21008209?v=4" width="100px;"/><br /><sub><b>yanglbme</b></sub>](https://github.com/yanglbme)<br />[💻](https://github.com/yanglbme/leetcode/commits?author=yanglbme "Code") </center> | <center> [<img src="https://avatars3.githubusercontent.com/u/21008209?v=4" width="100px;"/><br /><sub><b>yanglbme</b></sub>](https://github.com/yanglbme)<br />[💻](https://github.com/yanglbme/leetcode/commits?author=yanglbme "Code") </center> | <center> [<img src="https://avatars3.githubusercontent.com/u/21008209?v=4" width="100px;"/><br /><sub><b>yanglbme</b></sub>](https://github.com/yanglbme)<br />[💻](https://github.com/yanglbme/leetcode/commits?author=yanglbme "Code") </center> | 
-|---|---|---|---|---|---|---|
+| <center> [<img src="https://avatars3.githubusercontent.com/u/21008209?v=4" width="100px;"/><br /><sub><b>yanglbme</b></sub>](https://github.com/yanglbme)<br />[💻](https://github.com/yanglbme/leetcode/commits?author=yanglbme "Code") </center> | <center> [<img src="https://avatars3.githubusercontent.com/u/23625436?v=4" width="100px;"/><br /><sub><b>chakyam</b></sub>](https://github.com/chakyam)<br />[💻](https://github.com/yanglbme/leetcode/commits?author=chakyam "Code") </center> | 
+|---|---|
 
 <!-- ALL-CONTRIBUTORS-LIST:END -->

solution/021.Merge Two Sorted Lists/README.md

@@ -0,0 +1,40 @@
+## 合并两个有序链表
+### 题目描述
+
+将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。
+
+示例:
+```
+输入：1->2->4, 1->3->4
+输出：1->1->2->3->4->4
+```
+
+### 解法
+利用链表天然的递归性。如果 l1 为空，返回 l2；如果 l2 为空，返回 l1。如果 `l1.val < l2.val`，返回 l1->mergeTwoLists(l1.next, l2)；否则返回 l2->mergeTwoLists(l1, l2.next)。
+
+```java
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
+        if (l1 == null) {
+            return l2;
+        }
+        if (l2 == null) {
+            return l1;
+        }
+        if (l1.val < l2.val) {
+            l1.next = mergeTwoLists(l1.next, l2);
+            return l1;
+        }
+        l2.next = mergeTwoLists(l1, l2.next);
+        return l2;
+    }
+}
+```

solution/021.Merge Two Sorted Lists/Solution.java

@@ -0,0 +1,16 @@
+class Solution {
+    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
+        if (l1 == null) {
+            return l2;
+        }
+        if (l2 == null) {
+            return l1;
+        }
+        if (l1.val < l2.val) {
+            l1.next = mergeTwoLists(l1.next, l2);
+            return l1;
+        }
+        l2.next = mergeTwoLists(l1, l2.next);
+        return l2;
+    }
+}

solution/203.Remove Linked List Elements/README.md

@@ -30,4 +30,5 @@ class Solution {
         return head.val != val ? head : head.next;
     }
 }
-```
+```
+