Question 1

What is the prefix sum technique?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews — you should know arrays and loops.
**Difficulty:** Easy
**Language:** Python 3

> **How to read this doc:** Each 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 in the **Verified** section was produced by actually running the Python code with `python3 main.py`; nothing is quoted from memory.

## 1. Why This Even Matters — A

Question 2

How do you find the maximum subarray sum?

Accepted Answer

**Target Audience:** Beginners preparing for coding interviews; you should know arrays and loops.
**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 **Verified

Question 3

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 4

How do you count subarrays that sum to k?

Accepted Answer

**Target Audience:** Intermediate candidates — you should know arrays and hash maps; prefix sums are explained here and linked.
**Difficulty:** Medium
**Language:** Python 3

> **How to read this doc:** Each 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 in the **Verified** section was produced by actually running the Python code with `python3 main.py`; nothing is quoted from memory.

#

DATA STRUCTURES & ALGORITHMSDECODED.

Easy

What is the prefix sum technique?

Medium

How do you find the maximum subarray sum?

How do you solve the Gas Station problem?

How do you count subarrays that sum to k?