ghoshorn的专栏

Remove Nth Node From End of List   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

Longest Substring Without Repeating Characters Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters

Two Sum Given an array of integers, find two numbers such that they add up to a specific target number. The function twoSum should return indices of the two numbers such that they add up to th

4Sum 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:

Reverse Nodes in k-Group Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. If the number of nodes is not a multiple of k then left-out nodes i

Swap Nodes in Pairs   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 sho

Longest Common Prefix Write a function to find the longest common prefix string amongst an array of strings. 需要注意的特殊情况：输入是个空列表 import unittest class Solution: # @return a string def l

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

Median of Two Sorted Arrays There are two sorted arrays A and B of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).

Roman to Integer Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. 从字符串中每次处理一位，处理前需要先找到剩余串的枢纽（剩余串中最大的），以判断当前值在其左边还是右边，该相加还是相减。 i

Palindrome Number 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 yo

3Sum 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: Elements in a tr

Reverse digits of an integer. Example1: x = 123, return 321 Example2: x = -123, return -321 class Solution: # @return an integer def reverse(self, x): tmp=abs(x) if tm

Container With Most Water 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 lin

Longest Palindromic Substring Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindrom

leetcode中的两个 正则表达式匹配

Merge Two Sorted Lists   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. # Definition for sin

Generate Parentheses   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: "((()))", "(()

Merge k Sorted Lists Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. 可以通过leetcode 21的merge Two Lists来解决。 如果从头到尾依此合并，会超时。 改用分治法来调用。链表个数l>3时，

3Sum Closest 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 inpu

Letter Combinations of a Phone Number 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

Valid Parentheses Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the correct order, "()"

Remove Duplicates from Sorted Array   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

Substring with Concatenation of All Words You are given a string, S, and a list of words, L, that are all of the same length. Find all starting indices of substring(s) in S that is a concatenat

Implement strStr() Implement strStr(). Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. 要注意特殊情况，比如strstr("","") 应该等于0 =_= class

Remove Element   Given an array and a value, remove all instances of that value in place and return the new length. The order of elements can be changed. It doesn't matter what you leave be

Divide Two Integers   Divide two integers without using multiplication, division and mod operator. If it is overflow, return MAX_INT. class Solution1: # @return an integer def divi

数字转换为罗马数字

ZigZag Conversion 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)