add: 链表排序

src/list/sort-list.js

@@ -0,0 +1,31 @@
+import { mergeTwoLists } from './merge-two-sorted-lists'
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+export const sortList = function (head) {
+  if (head === null || head.next === null) return head
+
+  let slow = head
+  let fast = head
+  while (fast !== null) {
+    fast = fast.next
+    fast = fast !== null ? fast.next : null
+    if (fast !== null) {
+      slow = slow.next
+    }
+  }
+  const half = slow.next
+  slow.next = null
+  const left = sortList(head)
+  const right = sortList(half)
+  return mergeTwoLists(left, right)
+}