js-concepts: leetcode prob.876 - middle of the linked list

Author: baochau.dinh

LeetCode/876. Middle of the Linked List/index.js

@@ -0,0 +1,30 @@
+/**
+ * Given the head of a singly linked list, return the middle node of the linked list
+ */
+
+function ListNode(val, next = null) {
+  this.val = (val === undefined ? 0 : val);
+  this.next = (next === undefined ? null : next);
+}
+
+var middleNode = function(head) {
+  let length = 0;
+  let current = head;
+  while (current !== null) {
+    length++;
+    current = current.next;
+  }
+
+  let middleIdx = Math.floor(length / 2);
+  current = head;
+  let currIdx = 0;
+  while (currIdx < middleIdx) {
+    currIdx++;
+    current = current.next;
+  }
+
+  return current;
+}
+
+const listNode = new ListNode(1);
+console.log(middleNode(listNode));