摘要：
Given a linked list, remove the nth node from the end of list and return its head. For example, Note:Given n will always be valid.Try to do this in on 阅读全文
摘要：
Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array whic 阅读全文
摘要：
Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. 阅读全文
摘要：
Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of 阅读全文
摘要：
Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists. tag : du 阅读全文
摘要：
Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the 阅读全文
摘要：
Given two integers n and k, return all possible combinations of k numbers out of 1 ... n. For example, If n = 4 and k = 2, a solution is: 阅读全文
摘要：
Given a digit string, return all possible letter combinations that the number could represent. A mapping of digit to letters (just like on the telepho 阅读全文