Update 链表相关.md

blogs/Algorithm/剑指 Offer/链表相关.md

@@ -122,3 +122,50 @@ class Solution {
     }
 ```
 
+[25. 合并两个排序的链表](https://leetcode-cn.com/problems/he-bing-liang-ge-pai-xu-de-lian-biao-lcof/)
+
+```java
+class Solution {
+    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
+        ListNode h0 = new ListNode(0);
+        ListNode h = h0;
+        while (l1 != null && l2 != null) {
+            if (l1.val <= l2.val) {
+                h0.next = l1;
+                l1 = l1.next;
+            } else {
+                h0.next = l2;
+                l2 = l2.next;
+            }
+            h0 = h0.next;
+        }
+        if (l1 == null) {
+            h0.next = l2;
+        } else {
+            h0.next = l1;
+        }
+        return h.next;
+    }
+}
+```
+
+```java
+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;
+        } else {
+            l2.next = mergeTwoLists(l1, l2.next);
+            return l2;
+        }
+    }
+}
+```
+