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All Rights Reserved. https://pankajpipada.com/tech-interview-prep/algorithms/quick-notes/ Mon, 01 Jan 0001 00:00:00 +0000 https://pankajpipada.com/tech-interview-prep/algorithms/quick-notes/ <h1 id="algorithms-quick-notes">Algorithms: Quick Notes<a class="anchor" href="#algorithms-quick-notes">#</a></h1> <h2 id="bitmasks">Bitmasks<a class="anchor" href="#bitmasks">#</a></h2> <p>Bitmasking performs operations at the bit level (often faster and memory-efficient).</p> <ul> <li> <p>Commonly used for:</p> <ul> <li>subset representation (set of small integers),</li> <li>DP over subsets,</li> <li>toggling flags,</li> <li>fast membership checks.</li> </ul> </li> <li> <p>Quick patterns</p> <ul> <li>Iterate set bits: <code>while s: lsb = s &amp; -s; ...; s -= lsb</code></li> <li>Count bits: Python: <code>s.bit_count()</code></li> <li>Enumerate all subsets of a mask: <code>sub = mask; while sub: ...; sub = (sub - 1) &amp; mask</code> (also include <code>0</code> separately)</li> </ul> </li> </ul> <blockquote class='book-hint '> <p>Convention: <code>k</code> is 0-indexed from LSB (least-significant bit).</p> https://pankajpipada.com/tech-interview-prep/algorithms/problems/ Mon, 01 Jan 0001 00:00:00 +0000 https://pankajpipada.com/tech-interview-prep/algorithms/problems/ <h1 id="algorithms-problems">Algorithms: Problems<a class="anchor" href="#algorithms-problems">#</a></h1> <p>Approach problems by core Algorithms / techniques (DP/DFS/BFS/etc.).</p> <ul><li> <a href="#bfs">Bfs</a> (5) </li><li> <a href="#binary-search">Binary Search</a> (4) </li><li> <a href="#dfs">Dfs</a> (9) </li><li> <a href="#divide-and-conquer">Divide and Conquer</a> (2) </li><li> <a href="#dynamic-programming">Dynamic Programming</a> (14) </li><li> <a href="#greedy">Greedy</a> (1) </li></ul> <h2 id="bfs">Bfs</h2> <ul><li><a href="https://pankajpipada.com/tech-interview-prep/problems/binary-tree-level-order-traversal/">Binary tree level order traversal</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/clone-graph/">Clone graph</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/course-schedule/">Course schedule</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/number-of-islands/">Number of islands</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/pacific-atlantic-water-flow/">Pacific-Atlantic water flow</a></li></ul><h2 id="binary-search">Binary Search</h2> <ul><li><a href="https://pankajpipada.com/tech-interview-prep/problems/find-minimum-in-rotated-sorted-array/">Find minimum in rotated sorted array</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/kth-smallest-element-in-a-bst/">Kth smallest element in a BST</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/longest-increasing-subsequence/">Longest increasing subsequence</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/search-in-rotated-sorted-array/">Search in rotated sorted array</a></li></ul><h2 id="dfs">Dfs</h2> <ul><li><a href="https://pankajpipada.com/tech-interview-prep/problems/binary-tree-maximum-path-sum/">Binary tree maximum path sum</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/clone-graph/">Clone graph</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/construct-binary-tree-from-preorder-and-inorder-traversal/">Construct binary tree from preorder and inorder traversal</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/course-schedule/">Course schedule</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/maximum-depth-of-binary-tree/">Maximum depth of binary tree</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/number-of-islands/">Number of islands</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/pacific-atlantic-water-flow/">Pacific-Atlantic water flow</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/same-tree/">Same tree</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/validate-binary-search-tree/">Validate a binary search tree</a></li></ul><h2 id="divide-and-conquer">Divide and Conquer</h2> <ul><li><a href="https://pankajpipada.com/tech-interview-prep/problems/maximum-subarray/">Maximum subarray</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/merge-k-sorted-lists/">Merge k sorted lists</a></li></ul><h2 id="dynamic-programming">Dynamic Programming</h2> <ul><li><a href="https://pankajpipada.com/tech-interview-prep/problems/climbing-stairs/">Climbing stairs</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/coin-change/">Coin change</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/combination-sum-iv/">Combination sum IV</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/counting-bits/">Counting bits</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/decode-ways/">Decode ways</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/house-robber/">House robber</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/house-robber-ii/">House robber II</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/jump-game/">Jump game</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/longest-increasing-subsequence/">Longest increasing subsequence</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/longest-palindromic-substring/">Longest palindromic substring</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/maximum-subarray/">Maximum subarray</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/palindromic-substrings/">Palindromic substrings</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/unique-paths/">Unique paths</a></li><li><a href="https://pankajpipada.com/tech-interview-prep/problems/word-break/">Word break</a></li></ul><h2 id="greedy">Greedy</h2> <ul><li><a href="https://pankajpipada.com/tech-interview-prep/problems/non-overlapping-intervals/">Non overlapping intervals</a></li></ul>