Is Next Greater Node In Linked List easy or hard?

Next Greater Node In Linked List is rated Medium on LeetCode. The difficulty comes from recognizing the next greater element pattern and applying a monotonic stack to reduce the naive O(n²) approach to an O(n) solution.

Next Greater Node In Linked List Python/Java solution

Python and Java implementations typically convert the linked list to an array and then apply the monotonic stack technique. A stack tracks indices whose next greater value has not yet been found. When a larger value appears, the algorithm updates results for all smaller elements on the stack.

How to solve Next Greater Node In Linked List in O(n)?

First convert the linked list into an array of values. Traverse the array while maintaining a monotonic decreasing stack of indices. When the current value is greater than the value at the index on the stack top, pop that index and set its answer to the current value. Continue until the stack condition holds, then push the current index.

What is the best approach for Next Greater Node In Linked List?

The most efficient approach uses a monotonic stack after converting the linked list to an array. Iterate through the values while maintaining a decreasing stack of indices. When a larger value appears, pop indices from the stack and update their result. This processes each element once, giving O(n) time complexity.

Is Next Greater Node In Linked List asked at Google/Amazon/Meta?

Next greater element style problems are frequently asked in interviews at companies like Amazon, Google, and Meta. Variants involving arrays, stacks, and monotonic stacks appear regularly because they test pattern recognition and linear-time optimization techniques.

What data structure is used in Next Greater Node In Linked List?

The key data structure is a monotonic stack. It stores indices or values in decreasing order so that the next greater element can be determined efficiently. Arrays are also used after converting the linked list to allow indexed access.

What is the time complexity of Next Greater Node In Linked List?

The optimal solution runs in O(n) time where n is the number of nodes. Each node index is pushed to and popped from the stack at most once. The space complexity is O(n) for storing the array of values and the result array.

Description Hints 1 Solution Video 7:02

1019. Next Greater Node In Linked List

Medium64.6% acceptance4 companies

You are given the head of a linked list with n nodes.

For each node in the list, find the value of the next greater node. That is, for each node, find the value of the first node that is next to it and has a strictly larger value than it.

Return an integer array answer where answer[i] is the value of the next greater node of the i^th node (1-indexed). If the i^th node does not have a next greater node, set answer[i] = 0.

Example 1:

Input: head = [2,1,5]
Output: [5,5,0]

Example 2:

Input: head = [2,7,4,3,5]
Output: [7,0,5,5,0]

Constraints:

The number of nodes in the list is n.
1 <= n <= 10⁴
1 <= Node.val <= 10⁹

Asked at 4 companies

Microsoft Bloomberg

Google Amazon

Topics

Hints open one at a time

Hint 1

We can use a stack that stores nodes in monotone decreasing order of value. When we see a node_j with a larger value, every node_i in the stack has next_larger(node_i) = node_j .

7:02

Still stuck?Read 3 approaches, or watch a walkthrough.

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LanguageLoading editor…

1# Definition for singly-linked list.
2# class ListNode:
3#     def __init__(self, val=0, next=None):
4#         self.val = val
5#         self.next = next
6class Solution:
7    def nextLargerNodes(self, head: Optional[ListNode]) -> List[int]:
8        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2

Input

[2,1,5]

Input

[2,7,4,3,5]

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