Update 143-reorder-list.js

Author: everthis

143-reorder-list.js

@@ -1,3 +1,48 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {void} Do not return anything, modify head in-place instead.
+ */
+const reorderList = function(head) {
+  if(head == null) return head
+  let slow = head, fast = head
+  while(fast && fast.next) {
+    slow = slow.next
+    fast = fast.next.next
+  }
+  let head2 = reverse(slow.next)
+  slow.next = null
+  
+  while(head && head2) {
+    const next = head.next, next2 = head2.next
+    head2.next = head.next
+    head.next = head2
+    head = next
+    head2 = next2
+  }
+  
+  function reverse(node) {
+    let pre = null, cur = node
+    while(cur) {
+      const tmp = cur.next
+      cur.next = pre
+      pre = cur
+      cur = tmp
+    }
+    return pre
+  }
+};
+
+
+
+// another
+
 /**
  * Definition for singly-linked list.
  * function ListNode(val) {