> For the complete documentation index, see [llms.txt](https://blog.bernardw.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://blog.bernardw.com/problems.md).

# Problems

- [Lowest Common Ancestor of a Binary Tree](https://blog.bernardw.com/problems/lowest-common-ancestor-of-a-binary-tree.md)
- [Longest Substring Without Repeating Characters](https://blog.bernardw.com/problems/longest-substring-without-repeating-characters.md)
- [Longest Palindromic Substring](https://blog.bernardw.com/problems/longest-palindromic-substring.md)
- [Longest Common Prefix](https://blog.bernardw.com/problems/longest-common-prefix.md)
- [Isomorphic Strings](https://blog.bernardw.com/problems/isomorphic-strings.md)
- [Integer to Roman](https://blog.bernardw.com/problems/integer-to-roman.md)
- [Frog Jump](https://blog.bernardw.com/problems/frog-jump.md)
- [Find the Difference](https://blog.bernardw.com/problems/untitled-3.md)
- [Find k closest elements to a given value](https://blog.bernardw.com/problems/find-k-closest-elements-to-a-given-value.md)
- [Longest Common Subsequence](https://blog.bernardw.com/problems/longest-common-subsequence.md)
- [Binary Search Tree from Sorted Array](https://blog.bernardw.com/problems/binary-search-tree-from-sorted-array.md)
- [Balanced Binary Tree](https://blog.bernardw.com/problems/balanced-binary-tree.md)
- [Sort Using Two Stacks](https://blog.bernardw.com/problems/sort-using-two-stacks.md)
- [O(1) Stack](https://blog.bernardw.com/problems/o-1-stack.md)
- [k-th element to last of a LinkedList](https://blog.bernardw.com/problems/k-th-element-to-last-of-a-linkedlist.md): Implement an algorithm to find the kth to last element of a singly linked list
- [Dedup LinkedList](https://blog.bernardw.com/problems/dedup-linkedlist.md): Write code to remove duplicates from an unsorted linked list
- [Check Rotated String](https://blog.bernardw.com/problems/check-rotated-string.md): Find if a string is a rotation of another by using only one substring call
- [Compress String by Character Count](https://blog.bernardw.com/problems/compress-string-by-character-count.md): Compress string by character count
- [Escape HTML whitespace](https://blog.bernardw.com/problems/untitled-1.md): Escape white space with %20 in place
- [Check String Permutation](https://blog.bernardw.com/problems/check-string-permutation.md): Given two strings, write a method to decide if ones is a permutation of the other
- [Unique String](https://blog.bernardw.com/problems/unique-string.md): Implement an algorithm to determine if a string has all unique characters,What if you cannot use additional data structures?
- [Container With Most Water](https://blog.bernardw.com/problems/untitled-2.md)
- [4 Sum](https://blog.bernardw.com/problems/4-sum.md)
- [3 Sum Closest](https://blog.bernardw.com/problems/3sum-closest.md)
- [3 Sum](https://blog.bernardw.com/problems/3-sum.md)
- [2 Sum](https://blog.bernardw.com/problems/untitled.md)
- [Maximum Subarray](https://blog.bernardw.com/problems/maximum-subarray.md)
- [Nested List Weight Sum](https://blog.bernardw.com/problems/nested-list-weight-sum.md)
- [Palindrome Number](https://blog.bernardw.com/problems/palindrome-number.md)
- [Pow(x, n)](https://blog.bernardw.com/problems/pow-x-n.md)
- [Regular Expression Matching](https://blog.bernardw.com/problems/regular-expression-matching.md)
- [Remove Nth Node From End of List](https://blog.bernardw.com/problems/remove-nth-node-from-end-of-list.md)
- [Reverse Integer](https://blog.bernardw.com/problems/reverse-integer.md)
- [Roman to Integer](https://blog.bernardw.com/problems/roman-to-integer.md)
- [Rotate Array](https://blog.bernardw.com/problems/rotate-array.md)
- [Search a 2D Matrix](https://blog.bernardw.com/problems/search-a-2d-matrix.md)
- [Shortest Word Distance](https://blog.bernardw.com/problems/shortest-word-distance.md)
- [Two Sum III - Data structure design](https://blog.bernardw.com/problems/two-sum-iii-data-structure-design.md)
- [Valid Parentheses](https://blog.bernardw.com/problems/valid-parentheses.md)
- [ZigZag Conversion](https://blog.bernardw.com/problems/zigzag-conversion.md)
- [Quicksort](https://blog.bernardw.com/problems/quicksort.md)
- [Add Two Numbers](https://blog.bernardw.com/problems/add-two-numbers.md)
- [Best Time to Buy and Sell Stock](https://blog.bernardw.com/problems/best-time-to-buy-and-sell-stock.md)
- [Letter Combinations of a Phone Number](https://blog.bernardw.com/problems/letter-combinations-of-a-phone-number.md)