摘要： 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263/** * Definition for singly-linked list. * struct ListNode { * int val; * L... 阅读全文

摘要： Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.分析算法1：类似于归并排序，将Merge k 个的问题，拆分成Merge 2 个的子任务，然后递归回溯。算法复杂度 O(nlogn)算法2：使用最小堆。维护一个最大 大小 k 的最小堆，每次从堆顶pop出... 阅读全文

摘要： Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, given n = 3, a solution set is:[ "((()))", "(()())", "(())()", "()(())", "... 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.分析:就是使用两个指针，让较小的归并到新的list上：代码：方法一：1234567891011121314151617... 阅读全文

摘要： Given a linked list, remove the nth node from the end of list and return its head.For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node from the end, the linke... 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 correct order, "()" and "()[]{}" are all valid but ... 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 which gives the sum of target.Note: The solution set m... 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 telephone buttons) is given below.Input: Digit string "23"... 阅读全文

摘要： Write a function to find the longest common prefix string amongst an array of strings.1234567891011121314class Solution {public: string longestCommonPrefix(vector& strs) { if(strs.empty()) r... 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. You may assume that each input would have exactly... 阅读全文