WRITING
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Engineering write-ups — architecture, security, and the occasional war story.
#hash-map · All writing
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Tags
- #leetcode 50
- #array 13
- #dfs 11
- #bfs 9
- #dynamic-programming 9
- #recursion 9
- #trees 7
- #arrays 6
- #binary-search 6
- #hash-table 6
- #string 6
- #two-pointers 6
- #backtracking 4
- #dp 4
- #graphs 4
- #greedy 4
- #matrix 4
- #sliding-window 4
- #hash-map 3
- #heap-priority-queue 3
- #linked-list 3
- #stack 3
- #binary-search-tree 2
- #heap 2
- #math 2
- #memoization 2
- #priority-queue 2
- #sorting 2
- #strings 2
- #binary-tree 1
- #bit-manipulation 1
- #bucket-sort 1
- #counting 1
- #cycle-detection 1
- #divide-and-conquer 1
- #geometry 1
- #kadane 1
- #multi-source-bfs 1
- #prefix-sum 1
- #quickselect 1
- #simulation 1
- #string-matching 1
- #topological-sort 1
- #union-find 1
01
Clone Graph: deep-copying a cyclic structure without infinite loops
Cloning a graph means producing a fully independent copy of every node and every edge — but the graph has cycles, which means a naive recursive walk will loop forever. The fix is one hash map and a rule about when to register a clone.Jun 14, 2026 · 9 min read · #00046
02
Permutation in String: fixed-size window with a character count match
A permutation is just an anagram. So the question reduces to: does any window of length len(s1) in s2 have the same character frequencies as s1? A fixed-size sliding window with two frequency maps — or a single diff counter — answers it in O(n).Jun 13, 2026 · 15 min read · #00019
03
Minimum Window Substring: variable window with a coverage counter
The hard part isn't the window mechanics — it's knowing when the window is valid. A coverage counter that tracks how many characters in t are fully satisfied lets you shrink from the left the moment you have a valid window, without rechecking the whole map each time.Jun 13, 2026 · 13 min read · #00020
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