sort list

Author: dingjy94

algorithm/Sort/mergeSort/sortLinkedList.js

@@ -0,0 +1,56 @@
+/**
+ * lc148 Sort list (https://leetcode.com/problems/sort-list/)
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+const merge = (head1, head2) => {
+  let fake = new ListNode(null), head = fake;
+
+  while (head1 !== null && head2 !== null) {
+    if (head1.val < head2.val) {
+      head.next = head1;
+      head1 = head1.next;
+    } else {
+      head.next = head2;
+      head2 = head2.next;
+    }
+    head = head.next;
+  }
+
+  if (head1 !== null) {
+    head.next = head1;
+  }
+
+  if (head2 !== null) {
+    head.next = head2;
+  }
+
+  return fake.next;
+};
+
+var sortList = function (head) {
+  if (head === null || head.next === null) {
+    return head;
+  }
+
+  let slow = head, fast = head, prev = null;
+  while (fast !== null && fast.next !== null) {
+    prev = slow
+    slow = slow.next;
+    fast = fast.next.next;
+  }
+  prev.next = null;
+
+  const l1 = sortList(head);
+  const l2 = sortList(slow);
+
+  return merge(l1, l2);
+};
+

dataStructure/linkedList/README.md

@@ -1,5 +1,9 @@
 # Linked List
 
+## Some Tips
+### Get the middle point of linked list
+Use two pointers, one slow, one fast.
 
 ## Questions
 - [Remove Duplicates From Sorted List](https://leetcode.com/problems/remove-duplicates-from-sorted-list/)
+- [Sort List](https://leetcode.com/problems/sort-list/)