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Home Roadmap Visualizer & Lessons Dry-Run Engine Pricing Learning Path

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Introduction to strings

Understanding characters and bytes
Understanding the problem
How encodings change what length means
Overview of supported operations
Internal mechanics of strings
Working example

Immutability and building

Understanding the problem
The hidden cost of concatenation
How string builders avoid the cost
Repeat a string n times
Run length encoding

Pattern: Two pointers

Understanding the two pointer pattern
Identifying direct application
Reverse a string in place
Palindrome checker
Vowel exchange
Reverse words
Palindrome after one deletion

Pattern: Sliding window

Understanding the sliding window pattern
Carrying a frequency map in the window
Longest substring without repeats
Longest substring with k distinct characters
Permutation in a string
Minimum window substring

Pattern: Frequency counting

Understanding frequency counting
Choosing a canonical signature
Valid anagram
Group anagrams
First unique character

Pattern: Substring search

Understanding substring search
Why brute force degrades to O(N·M)
Building the prefix function
Find the first occurrence
Detect a repeated pattern

Pattern: Parsing and partitioning

Understanding parse-as-you-scan
Validate a number
Partition labels
Decode a nested string

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First unique character

First unique character

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