<h1 id="patterns">Patterns<a aria-hidden="true" class="anchor-heading icon-link" href="#patterns"></a></h1>
If input array is sorted then
<ul>
<li>Binary search</li>
<li>Two pointers</li>
</ul>
If asked for all permutations/subsets then
<ul>
<li>Backtracking</li>
</ul>
If given a tree then
<ul>
<li>DFS</li>
<li>BFS</li>
</ul>
If given a graph then
<ul>
<li>DFS</li>
<li>BFS</li>
</ul>
If given a linked list then
<ul>
<li>Two pointers</li>
</ul>
If recursion is banned then
<ul>
<li>Stack</li>
</ul>
If must solve in-place then
<ul>
<li>Swap corresponding values</li>
<li>Store one or more different values in the same pointer</li>
</ul>
If asked for maximum/minimum subarray/subset/options then
<ul>
<li>Dynamic programming</li>
</ul>
If asked for top/least K items then
<ul>
<li>Heap</li>
<li>QuickSelect</li>
</ul>
If asked for common strings then
<ul>
<li>Map</li>
<li>Trie</li>
</ul>
Else
<ul>
<li>Map/Set for O(1) time &#x26; O(n) space</li>
<li>Sort input for O(nlogn) time and O(1) space</li>
</ul>
Reference: <a href="https://seanprashad.com/leetcode-patterns/">https://seanprashad.com/leetcode-patterns/</a>

Patterns

notes


Hi! I am Pushkar! This is a place for my personal notes.

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