feat: 2025-10-27打卡

148.sort-list.java

@@ -0,0 +1,63 @@
+/*
+ * @lc app=leetcode id=148 lang=java
+ *
+ * [148] Sort List
+ */
+
+// @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 sortList(ListNode head) {
+        if(head == null || head.next == null) {
+            return head;
+        }   
+        ListNode slow = head, fast = head, prev = null;
+        while(fast != null && fast.next != null) {
+            fast = fast.next.next;
+            prev = slow;
+            slow = slow.next;
+        }
+        prev.next = null;
+        ListNode l1 = sortList(head);
+        ListNode l2 = sortList(slow);
+        return merge(l1, l2);
+    }
+
+    private ListNode merge(ListNode l1, ListNode l2) {
+        ListNode dummy = new ListNode(0), tail = dummy, tmp;
+        dummy.next = null;
+        while(l1 != null || l2 != null) {
+            if(l1 == null || l2 == null) {
+                if(l1 != null) {
+                    tail.next = l1;
+                } else {
+                    tail.next = l2;
+                }
+                break;
+            } else {
+                if(l1.val <= l2.val) {
+                    tmp = l1;
+                    l1 = l1.next;
+                } else {
+                    tmp = l2;
+                    l2 = l2.next;
+                }
+            }
+            tail.next = tmp;
+            tail = tail.next;
+            tail.next = null;
+        }
+        return dummy.next;
+    }
+}
+// @lc code=end
+