Microsoft·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Apr 2026

Summary

Microsoft SWE coding round, just one problem on linked list reordering. Short and to the point, not much else to say about it.

Questions Asked (1)

Given a linked list, reorder it in a specific pattern (e.g. L0 -> Ln -> L1 -> Ln-1 -> ...).

Algorithms & Data Structures

Author's notes

Classic linked list manipulation.

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AI HintsAI Generated

Suggested Approach

Break the problem into three clear phases: find the middle of the linked list, reverse the second half, and then merge the two halves alternately. This approach achieves O(n) time and O(1) space, which is optimal. Walk through a small example to verify correctness and discuss edge cases like odd/even length and single node.

Pro tip: Mention that this is a common pattern for reordering lists and that the same technique applies to problems like palindrome checking. Also, explicitly state the time and space complexity and compare with a naive approach that uses extra space.

1. Find the middle of the linked list

Use the slow and fast pointer technique (tortoise and hare) to find the middle node. This splits the list into two halves, with the second half starting from the node after the middle (for even length) or the middle node itself (for odd length).

2. Reverse the second half

Reverse the second half of the linked list in-place using iterative pointer manipulation. This allows us to access nodes from the end in the correct order for merging.

3. Merge the two halves alternately

Merge the first half and the reversed second half by interleaving nodes: take one node from the first half, then one from the second, and so on. Adjust pointers carefully to avoid cycles.

4. Handle edge cases and verify

Consider edge cases: empty list, single node, two nodes, odd/even length. Walk through an example to ensure the reordering is correct and no nodes are lost or cycles created.

Key Points to Mention

Time complexity: O(n) because we traverse the list a constant number of times.
Space complexity: O(1) because we only use pointers, no extra data structures.
Slow and fast pointer technique for finding the middle.
In-place reversal of a linked list using iterative pointer manipulation.
Merging two lists by alternating nodes without creating cycles.
Edge cases: empty list, single node, two nodes, odd/even length.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.