🧮Algorithm

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2026-07-23
Breaking Down the Graph Family: Course Schedule to Clone Graph to Word Ladder— Kahn's algorithm for detecting cycles, a dictionary that doubles as both a visited-check and a lookup table, and a word game that turns out to be BFS in disguise — all reusing the same snapshot-queue engine from grid BFS.
#algorithm#graph#bfs#dfs#leetcode#python
12 min read
2026-07-20
Breaking Down the Tree Family: Level Order to Validate BST to LCA— Grid BFS's snapshot trick reused on trees, four ways to validate a BST, and a lowest-common-ancestor algorithm that turns out to be the same trick as linked list intersection wearing a different hat.
#algorithm#tree#bst#bfs#dfs#leetcode#python
9 min read
2026-07-17
Breaking Down Grid BFS— Four problems, one skeleton — Number of Islands, Max Area, Rotting Oranges, and Flood Fill. Learn the skeleton once, then track only what changes.
#algorithm#bfs#graph#leetcode#python
8 min read
2026-07-17
Breaking Down the Interval Family: Merge Intervals to Meeting Rooms III— One family, one first move — sort by start. Then it branches: merge into blobs, count with a sweep or a bucket array, keep room identities with a heap, add passenger weights, or juggle two heaps when a delayed meeting needs a specific room. The question that splits every follow-up: do you need WHO, or just HOW MANY?
#algorithm#intervals#heap#sweep-line#leetcode#python
13 min read
2026-07-17
Breaking Down the Stack Family: Valid Parentheses to LRU Cache— Counters vs stacks, why Min Remove stores indexes, Min Stack three ways, and the design story behind LRU Cache — a hashmap that answers 'where' married to a linked list that answers 'who's oldest'.
#algorithm#stack#design#leetcode#python
10 min read
2026-07-15
Breaking Down Number of Islands— LeetCode #200 — the grid traversal pattern behind so many interview problems, and why I picked BFS over recursive DFS.
#algorithm#bfs#dfs#graph#leetcode
4 min read
2026-06-03
Breaking Down Stock Trading DP— From one trade to multiple trades to cooldown — same pattern, different constraints
#leetcode#algorithm#dynamic-programming#greedy
4 min read
2026-06-02
Breaking Down Two Sum— LeetCode #1 Two Sum — there's more to it than just HashMap
#algorithm#two-pointer#hashmap#leetcode
5 min read
2026-06-01
Breaking Down Sliding Window— A technique that turns O(n²) subarray problems into O(n) by maintaining two pointers that define a moving window.
#today-i-learned#algorithm#sliding-window#python
5 min read