Algorithm Atlas

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Learn Strings with visual DSA lessons

Learn Strings with 2 DSA patterns and 11 visual lessons. Follow step-by-step animations and synced C#, Python, and Java code.

A string is a row of characters used to store words, sentences, and other text.

Two-Pointer (Palindrome)

Compare letters from both ends and move toward the middle.

Reverse a String Easy · Swap from both ends
Valid Palindrome Easy · Compare matching ends
Valid Palindrome II Easy · Allow one skipped letter
Longest Palindromic Substring Medium · Expand from a center
Palindromic Substrings Medium · Count every center expansion

Sliding Window (String)

Move a group of nearby letters while tracking their counts.

Find All Anagrams in a String Medium · Fixed-size letter window
Longest Substring Without Repeating Characters Medium · Shrink when a letter repeats
Longest Substring with K Uniques Medium · Keep exactly K letter types
Permutation in String Medium · Look for one matching window
Minimum Window Substring Hard · Grow to valid, shrink to smallest
Substring with Concatenation of All Words Hard · Slide in whole-word steps