Merge K Sorted Lists
Explore how to merge k sorted singly linked lists into a single sorted linked list. Understand the problem constraints and develop a clear solution strategy using C++ to efficiently combine multiple sorted lists. This lesson helps you grasp the techniques and coding patterns essential for solving k-way merge problems in coding interviews.
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Statement
You are given an array, lists, containing k singly linked lists. Each of these linked lists is individually sorted in ascending order.
Your task is to merge all k linked lists into a single sorted linked list in ascending order and return the merged list.
Constraints:
klists.lengthklists[i].lengthlists[i][j]Each
lists[i]is sorted in ascending order.The sum of all
lists[i].lengthwill not exceed.
Examples
Understand the problem
Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:
Merge K Sorted Lists
What is the output if the following array is given as input?
lists = [
1 → 2 → 3 → NULL,
12 → 56 → 200 → NULL,
-10 → -2 → 5 → NULL
]
1 → 2 → 3 → 12 → 56 → 200 → -10 → -2 → 5 → NULL
1 → 2 → 3 → -10 → -2 → 5 → 12 → 56 → 200 → NULL
-10 → -2 → 1 → 2 → 3 → 5 → 12 → 56 → 200 → NULL
-10 → -2 → 5 → 1 → 2 → 3 → 12 → 56 → 200 → NULL
Figure it out!
We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.
Try it yourself
Implement your solution in the following coding playground.
// Definition for a Linked List node// class ListNode {// public:// int val;// ListNode* next;// // Constructor// ListNode(int val = 0, ListNode* next = nullptr);// };ListNode* MergeKLists(vector<ListNode*> lists) {// Replace this placeholder return statement with your codereturn nullptr;}