Given a directed graph, find a topological order of the graph.
Given a string, validate that it is a valid number.
Given an absolute path for a file (Unix-style), simplify it.
Given an unsorted array of integers, find the length of the longest consecutive elements sequence.
Sort a linked list in O(n log n) time using constant space complexity.
Given a linked list, return the node where the cycle begins.
Given three strings:
s3, determine whether
s3 is formed by the interleaving of
Print numbers from 1 to the largest number with
n digits by recursion.
Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.
Given a string of digits, excluding 0 and 1, return all possible letter combinations that the number could represent.