LZTree的专栏

Description:The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)P A

题目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

题目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

题目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.算法思想：比较两个已排序的链表的第一个元素，哪一个链表第一个元素小则添加到新的链表中去，并

Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find

题目：Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.Subscribe to see which companies asked this question.算法思想：     针对K个排序的链表进行两

题目：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:[  "((()))",  "(()())",  "(())

题目：Given a linked list, swap every two adjacent nodes and return its head.For example,Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only constant

题目：Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.k is a positive integer and is less than or equal to the length of the linked list. If the

题目：Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.Do not allocate extra space for another array, you must do this in p

题目：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 s

题目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:

题目：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

原题：Given an array of integers, return indices of the two numbers such that they add up to a specific target.You may assume that each input would have exactly one solution, and you may not use th

Description:You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two number

Description:Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321click to show spoilers.Have you thought about this?Here are some good questions

Implement atoi to convert a string to an integer.Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input ca

Given an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999.求出所给数字的个、十、百、千位上的数字，然后对应到相应罗马数字字符class Solution {public:    string intToRoman(

Given a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.针对罗马字符出现的每个位上所有情况考虑进去，得到相应整形数字class Solution {public:    int romanToInt(string

Write a function to find the longest common prefix string amongst an array of strings.算法思想：逐个比对每个字符串的前缀字符，若出现不相等或者其中某个字符已经是最末尾的字符时，跳出循环。C++实现如下：#include #include using namespace std;class

Determine whether an integer is a palindrome. Do this without extra space.click to show spoilers.Some hints:Could negative integers be palindromes? (ie, -1)If you are thinking of converting th

题目：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 zero.Note: The solution set must not

题目：Given an array and a value, remove all instances of that value in place and return the new length.Do not allocate extra space for another array, you must do this in place with constant me