2025-05-17提交

21.merge-two-sorted-lists.java

@@ -0,0 +1,59 @@
+/*
+ * @lc app=leetcode id=21 lang=java
+ *
+ * [21] Merge Two Sorted Lists
+ */
+
+// @lc code=start
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
+        if(list1 == null || list2 == null) {
+            return list1 == null?list2:list1;
+        }
+        ListNode h = null, cur = null;
+        while(list1 != null && list2!=null) {
+            if(list1.val <= list2.val) {
+                if(h == null) {
+                    h = cur = list1;
+                    list1 = list1.next;
+                    h.next = null;
+                } else {
+                    cur.next = list1;
+                    list1 = list1.next;
+                    cur = cur.next;
+                    cur.next = null;
+                }
+            } else {
+                if(h == null) {
+                    h = cur = list2;
+                    list2 = list2.next;
+                    h.next = null;
+                } else {
+                    cur.next = list2;
+                    list2 = list2.next;
+                    cur = cur.next;
+                    cur.next = null;
+                }
+            }
+        }
+        if (list1 !=null) {
+            cur.next = list1;
+        }
+        if(list2 != null) {
+            cur.next = list2;
+        }
+        return h;
+    }
+}
+// @lc code=end
+