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Coding & Algorithms questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master coding & algorithms interviews.

What difficulty level is this interview question?

This is a hard difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Two Sigma.

What role is this question designed for?

This question is commonly asked for Data Scientist candidates at Two Sigma during technical interviews.

Merge Two Sorted Lists

Last updated: Mar 29, 2026

Quick Overview

This question evaluates proficiency with linked list data structures, pointer manipulation, in-place merging of sorted sequences, and general algorithmic reasoning within the Coding & Algorithms domain.

Two Sigma

Mar 18, 2026, 12:00 AM

Data Scientist

Technical Screen

Coding & Algorithms

You are given the heads of two singly linked lists, each already sorted in non-decreasing order. Merge them into one sorted linked list and return the head of the merged list.

Requirements:

Reuse the existing nodes if possible.
The output must also be sorted in non-decreasing order.
Handle the case where one or both input lists are empty.

Example:

List A: 1 -> 2 -> 4
List B: 1 -> 3 -> 4
Output: 1 -> 1 -> 2 -> 3 -> 4 -> 4

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