# Problems

- [Lowest Common Ancestor of a Binary Tree](/problems/lowest-common-ancestor-of-a-binary-tree.md)
- [Longest Substring Without Repeating Characters](/problems/longest-substring-without-repeating-characters.md)
- [Longest Palindromic Substring](/problems/longest-palindromic-substring.md)
- [Longest Common Prefix](/problems/longest-common-prefix.md)
- [Isomorphic Strings](/problems/isomorphic-strings.md)
- [Integer to Roman](/problems/integer-to-roman.md)
- [Frog Jump](/problems/frog-jump.md)
- [Find the Difference](/problems/untitled-3.md)
- [Find k closest elements to a given value](/problems/find-k-closest-elements-to-a-given-value.md)
- [Longest Common Subsequence](/problems/longest-common-subsequence.md)
- [Binary Search Tree from Sorted Array](/problems/binary-search-tree-from-sorted-array.md)
- [Balanced Binary Tree](/problems/balanced-binary-tree.md)
- [Sort Using Two Stacks](/problems/sort-using-two-stacks.md)
- [O(1) Stack](/problems/o-1-stack.md)
- [k-th element to last of a LinkedList](/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](/problems/dedup-linkedlist.md): Write code to remove duplicates from an unsorted linked list
- [Check Rotated String](/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](/problems/compress-string-by-character-count.md): Compress string by character count
- [Escape HTML whitespace](/problems/untitled-1.md): Escape white space with %20 in place
- [Check String Permutation](/problems/check-string-permutation.md): Given two strings, write a method to decide if ones is a permutation of the other
- [Unique String](/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](/problems/untitled-2.md)
- [4 Sum](/problems/4-sum.md)
- [3 Sum Closest](/problems/3sum-closest.md)
- [3 Sum](/problems/3-sum.md)
- [2 Sum](/problems/untitled.md)
- [Maximum Subarray](/problems/maximum-subarray.md)
- [Nested List Weight Sum](/problems/nested-list-weight-sum.md)
- [Palindrome Number](/problems/palindrome-number.md)
- [Pow(x, n)](/problems/pow-x-n.md)
- [Regular Expression Matching](/problems/regular-expression-matching.md)
- [Remove Nth Node From End of List](/problems/remove-nth-node-from-end-of-list.md)
- [Reverse Integer](/problems/reverse-integer.md)
- [Roman to Integer](/problems/roman-to-integer.md)
- [Rotate Array](/problems/rotate-array.md)
- [Search a 2D Matrix](/problems/search-a-2d-matrix.md)
- [Shortest Word Distance](/problems/shortest-word-distance.md)
- [Two Sum III - Data structure design](/problems/two-sum-iii-data-structure-design.md)
- [Valid Parentheses](/problems/valid-parentheses.md)
- [ZigZag Conversion](/problems/zigzag-conversion.md)
- [Quicksort](/problems/quicksort.md)
- [Add Two Numbers](/problems/add-two-numbers.md)
- [Best Time to Buy and Sell Stock](/problems/best-time-to-buy-and-sell-stock.md)
- [Letter Combinations of a Phone Number](/problems/letter-combinations-of-a-phone-number.md)