Strings - Complete Edition - Kotlin Edition

Stop memorizing string solutions. Start seeing why they work.

Strings - Complete Edition - Kotlin Edition brings both volumes together: 102 string algorithms taught through plain-language explanations, Kotlin implementations, and step-by-step visual walkthroughs that trace the index, the window, the stack, and the trie through every step. Every algorithm is shown in full color, so characters, windows, and counts stand apart at a glance and are easy to trace.

Watch a stack validate nested brackets. Follow a sliding window across a string. See a trie grow one character at a time, and track a DP table as it measures the distance between two words. Instead of holding every changing index in your head, follow the execution on the page.

The visual walkthroughs use small multiples, a data visualization technique that presents successive stages of an algorithm as a series of consistently structured diagrams. By seeing meaningful stages together, you can compare states, follow what moves, and understand how each decision affects the next. This brings the algorithm to life, reinforcing understanding and helping the underlying patterns and mechanics stay with you longer.

Every main algorithm is presented in three complementary parts:

Understanding & Reasoning: Learn the goal, key idea, edge cases, and time and space complexity before studying the implementation.

Inspect & Debug: Examine Kotlin code alongside an AI-Era Interview Lens that challenges you to question assumptions, recognize plausible mistakes, and explain why a solution is correct.

Trace & Walkthrough: Follow the input through intermediate states to the result, with visual explanations of the decisions that matter.

The nine core patterns cover Parentheses & Stack; Sliding Window; Anagrams & Character Frequency; Palindromes; Permutations, Combinations & Backtracking; Encoding & In-Place Manipulation; Pattern Matching; and Tries, Dictionaries & Word Structures - plus Dynamic Programming for Subsequences & Edit Distance. Along the way you'll build real fluency in selection, insertion, merge, and quick sort, then carry that same rigor into stacks, tries, and DP tables.

There's an old engineering joke: reach for a regular expression to solve a string problem, and you may walk away with two problems instead of one. This book is about building the instincts that tell you which one you actually need.

Every code sample was compiled, tested against edge cases beyond what's printed on the page, and independently reviewed before making it into the book.

Designed for readers with basic Kotlin knowledge who want to strengthen coding interview preparation, debugging, and algorithmic reasoning.

This Complete Edition contains every algorithm from Strings - Volume 1 and Strings - Volume 2 - Kotlin Edition in a single book.

Understand the idea. Follow the state. Explain the result.