Question 1

How do you find the best time to buy and sell a stock?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you only need to know loops and variables in Python.  
**Difficulty:** Easy  
**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, and the output you

Question 2

How do you solve the 0/1 knapsack problem?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you need loops, lists and 2D lists.  
**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, and the output you see in the **V

Question 3

What is a greedy algorithm?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you should know lists, loops and functions in Python; everything else is explained.  
**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

Question 4

How do you solve the house robber problem?

Accepted Answer

**Target Audience:** Beginners who have seen climbing stairs and want the next dynamic programming step.
**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, and the output you see in the **V

Question 5

How do you solve the Gas Station problem?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you should know lists, loops and functions in Python; everything else is explained.  
**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

Question 6

How do you solve the coin change problem?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you need loops, arrays and a first idea of what dynamic programming is.  
**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 ru

Question 7

How do you solve the Jump Game?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you should know lists, loops and functions in Python; everything else is explained.  
**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

Question 8

How does Dijkstra's algorithm work?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — no graph-algorithm background assumed
**Difficulty:** Hard
**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

Imagin

DATA STRUCTURES & ALGORITHMSDECODED.

Easy

How do you find the best time to buy and sell a stock?

Medium

How do you solve the 0/1 knapsack problem?

What is a greedy algorithm?

How do you solve the house robber problem?

How do you solve the Gas Station problem?

How do you solve the coin change problem?

How do you solve the Jump Game?

Hard

How does Dijkstra's algorithm work?