Topological Sorting
Given a directed graph, find a topological order of the graph.
Valid Number
Given a string, validate that it is a valid number.
Simplify Path
Given an absolute path for a file (Unix-style), simplify it.
Longest Consecutive Sequence
Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
Sort List
Sort a linked list in O(n log n) time using constant space complexity.
Linked List Cycle II
Given a linked list, return the node where the cycle begins.
Interleaving String
Given three strings: s1, s2, s3, determine whether s3 is formed by the interleaving of s1 and s2.
Print Numbers by Recursion
Print numbers from 1 to the largest number with n digits by recursion.
Remove Duplicates from Sorted List II
Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
Letter Combinations of a Phone Number
Given a string of digits, excluding 0 and 1, return all possible letter combinations that the number could represent.