Interview Training: Strings
[!NOTE] This module explores the core principles of Interview Training: Strings, deriving solutions from first principles and hardware constraints to build world-class, production-ready expertise.
1. Reaching the Next Level
You have now mastered the Core Fundamentals of Strings:
- Encoding, Character searching, and standard manipulation.
- Sliding Window applied to strings.
- Frequency Counting and Palindromes.
- Tries (Prefix Trees).
However, Strings are notoriously difficult in interviews because they often require complex simulation, parsing, or combinatorial math.
2. Welcome to The Problem Vault
To keep this core curriculum concise and focused on engineering principles, all highly specific string simulations and tricky edge cases are stored in The Problem Vault.
The Vault contains complete, Gold Standard deep-dives for specific problems, featuring interactive visualizers and rigorous hardware analysis.
String Simulation & Parallel Replacement
When modifying strings, doing it sequentially often destroys the index mapping.
- Find And Replace in String: Master parallel simulation using auxiliary mapping arrays to safely replace multiple substrings without mutating the original string directly.
Combinatorics & Modulo Math
When building strings based on constrained permutations.
- Next Closest Time: Learn how to bound brute force to O(1) operations and use Modulo Arithmetic to calculate time-deltas seamlessly across midnight.
Parsing & Run-Length Encoding (RLE)
When characters repeat, compressing the string simplifies the logic.
- Expressive Words: Learn how to extract Character DNA (RLE) to compare “stretchy” words, and learn the massive latency jump between Object Allocation vs Four-Pointer O(1) optimization.
[!TIP] How to Practice Try to solve the problem on LeetCode first. If you get stuck for more than 20 minutes, open the associated Vault chapter. Do not look at the code yet. Read the “Intuition Through Analogy” section and play with the Visualizer, then try to code it again.