dsa1 min read
Count Distinct Substrings — Suffix Trie / Rolling Hash
Count distinct substrings. Naive: insert all suffixes into trie and count nodes. Optimal: suffix automaton or rolling hash.
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dsa3 min read
Tries — Master Recap & Cheatsheet
Complete Tries cheatsheet: core operations, 5 patterns, binary trie for XOR, complexity table, and decision guide.
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dsa7 min read
Two Pointers & Sliding Window — Complete Guide (Problems 101–160)
Master Two Pointers and Sliding Window patterns with 60 problems, 5-language solutions, and MAANG company tags.
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Valid Palindrome [Easy] — Two Pointers Inward
Check if a string is a palindrome after removing non-alphanumeric characters using inward two pointers.
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Reverse String [Easy] — Two Pointers In-Place Swap
Reverse an array of characters in-place using the classic two-pointer swap technique.
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