leetcode.148

Author: tiny1990

README.md

@@ -82,4 +82,5 @@ $ 现在开始，分Tag笔记做过的题
 92   |https://leetcode-cn.com/problems/reverse-linked-list-ii/                     | [反转链表 II](./linkedlist_array/92.反转链表II)
 141  |https://leetcode-cn.com/problems/linked-list-cycle/                          | [环形链表](./linkedlist_array/141.环形链表)
 142  |https://leetcode-cn.com/problems/linked-list-cycle-ii/                       | [环形链表 II](./linkedlist_array/142.环形链表II)
-143  |https://leetcode-cn.com/problems/reorder-list/                               | [重排链表](./linkedlist_array/143.重排链表)
+143  |https://leetcode-cn.com/problems/reorder-list/                               | [重排链表](./linkedlist_array/143.重排链表)
+148  |https://leetcode-cn.com/problems/sort-list/                                  | [排序链表](./linkedlist_array/148.排序链表)

linkedlist_array/148.排序链表/README.md

@@ -0,0 +1,78 @@
+# 148. 排序链表
+在 O(n log n) 时间复杂度和常数级空间复杂度下，对链表进行排序。  
+
+示例 1:
+```
+输入: 4->2->1->3
+输出: 1->2->3->4
+```
+示例 2:
+```
+输入: -1->5->3->4->0
+输出: -1->0->3->4->5
+```
+```go
+func sortList(head *ListNode) *ListNode {
+}
+```
+
+## 解题思路
+二分法
+
+## 题解
+
+```go
+func sortList(head *ListNode) *ListNode {
+    if head == nil || head.Next == nil {
+        return head
+    }
+    mid := findMid(head)
+    right := sortList(mid.Next)
+    mid.Next = nil
+
+    left := sortList(head)
+    
+    return  merge(left , right)
+
+}
+
+func merge(list1, list2 *ListNode) *ListNode {
+
+    dummy := &ListNode{}
+    tail := dummy
+
+    for list1 != nil && list2 != nil {
+        if list1.Val > list2.Val {
+            tail.Next = list2
+            list2 = list2.Next
+        } else {
+            tail.Next = list1
+            list1 = list1.Next
+        }
+        tail = tail.Next
+    }
+
+    if list1 != nil {
+        tail.Next = list1
+    }
+
+    if list2 != nil {
+        tail.Next = list2
+    }
+
+    return dummy.Next
+
+}
+
+func findMid(head *ListNode) *ListNode {
+    slow := head
+    fast := head.Next
+
+    for fast != nil && fast.Next != nil {
+        slow = slow.Next
+        fast = fast.Next.Next
+    }
+    return slow
+}
+
+```