Question 1

How do you reverse a linked list?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — no prior algorithms knowledge assumed
**Difficulty:** Easy
**Language:** Python 3

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. All code is Python, and every output block in the **Verified** section was copied from a real run of the examples on this page.

## 1. Why This Even Matters — A Story First

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Question 2

What is the fast and slow pointer technique?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — no prior algorithms knowledge assumed
**Difficulty:** Easy
**Language:** Python 3

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. All code is Python, and every output block in the **Verified** section was copied from a real run of the examples on this page.

## 1. Why This Even Matters — A Story First

A tort

Question 3

How do you find the intersection node of two linked lists?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you should know what a linked list node is; everything else is explained
**Difficulty:** Easy
**Language:** Python 3

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. All code is Python, and every output block in the **Verified** section was copied from a real run of the examples on this page.

## 1. Why This E

Question 4

How do you find the middle of a linked list?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — no prior algorithms knowledge assumed
**Difficulty:** Easy
**Language:** Python 3

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. All code is Python, and every output block in the **Verified** section was copied from a real run of the examples on this page.

## 1. Why This Even Matters — A Story First

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Question 5

How do you move all zeroes to the end of an array in place?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — no prior algorithms knowledge assumed
**Difficulty:** Easy
**Language:** Python 3

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. All code is Python, and every output block in the **Verified** section was copied from a real run of the examples on this page.

## 1. Why This Even Matters — A Story First

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Question 6

How do you check if a string is a valid palindrome?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — no prior algorithms knowledge assumed
**Difficulty:** Easy
**Language:** Python 3

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. All code is Python, and every output block in the **Verified** section was copied from a real run of the examples on this page.

## 1. Why This Even Matters — A Story First

A sign

Question 7

How do you check if a linked list is a palindrome?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you should know what a linked list node is; everything else is explained
**Difficulty:** Easy
**Language:** Python 3

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. All code is Python, and every output block in the **Verified** section was copied from a real run of the examples on this page.

## 1. Why This E

Question 8

How do you solve the Two Sum problem efficiently?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you know basic Python lists and loops; nothing else assumed.
**Difficulty:** Easy
**Language:** Python 3

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Every output shown was produced by actually running the code with `python3` (3.13); nothing is typed in by hand.

## 1. Why This Even Matters — A Story Firs

Question 9

How do you remove the nth node from the end of a linked list?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you should know what a linked list node is; everything else is explained
**Difficulty:** Medium
**Language:** Python 3

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. All code is Python, and every output block in the **Verified** section was copied from a real run of the examples on this page.

## 1. Why This

Question 10

How do you get the right-side view of a binary tree?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you should know what a binary tree is; BFS and DFS are explained here.  
**Difficulty:** Medium  
**Language:** Python 3

> **How to read this doc:** every idea is explained in plain words first. When a word appears that an interviewer will expect you to know, it is tagged `📌 Interview term:` with a one-line definition, and every tagged term is collected in the Quick Glossary at the end. Every program on this page was actually run

DATA STRUCTURES & ALGORITHMSDECODED.

Easy

How do you reverse a linked list?

What is the fast and slow pointer technique?

How do you find the intersection node of two linked lists?

How do you find the middle of a linked list?

How do you move all zeroes to the end of an array in place?

How do you check if a string is a valid palindrome?

How do you check if a linked list is a palindrome?

How do you solve the Two Sum problem efficiently?

Medium

How do you remove the nth node from the end of a linked list?

How do you get the right-side view of a binary tree?

How do you find the node where a linked list cycle begins?

How do you detect a cycle in a linked list?

How do you solve the container with most water problem?

Trapping Rain Water with two pointers — why does leftMax/rightMax work in O(1) space?

How do you solve the 3Sum problem?

How do you find the longest increasing subsequence?

Hard

How do you solve the trapping rain water problem?