Merge k Sorted Lists problem solved

Author: hasibulislam999

Merge Sort/23_merge-k-sorted-lists.js

@@ -0,0 +1,39 @@
+/**
+ * Title: Merge k Sorted Lists
+ * Description: You are given an array of k linked-lists lists, each linked-list is sorted in ascending order. Merge all the linked-lists into one sorted linked-list and return it.
+ * Author: Hasibul Islam
+ * Date: 10/04/2023
+ */
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode[]} lists
+ * @return {ListNode}
+ */
+const mergeKLists = (lists) => {
+  let arr = [];
+
+  //flatten
+  function addNode(node) {
+    if (node != null) {
+      arr.push(node);
+      addNode(node.next);
+      node.next = null; //prevent leetcode Javascript heap out of memory
+    }
+  }
+  lists.forEach(addNode);
+
+  //sort
+  if (arr.length > 1) {
+    arr.sort((a, b) => a.val - b.val);
+    arr.reduce((a, b) => (a.next = b));
+  }
+
+  return arr.length != 0 ? arr[0] : null;
+};