Felomeng的技术博客

Search for a Range MediumGiven an array of integers sorted in ascending order, find the starting and ending position of a given target value.Your algorithm's runtime complexity must be in the o...

Search in Rotated Sorted Array MediumSuppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.(i.e.,0 1 2 4 5 6 7might become4 5 6 7 0 1 2).You are giv...

Longest Valid Parentheses HardGiven a string containing just the characters'('and')', find the length of the longest valid (well-formed) parentheses substring.For"(()", the longest valid pa...

Next Permutation MediumImplement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.If such arrangement is not possible, it must rearrange...

Substring with Concatenation of All Words HardYou are given a string,s, and a list of words,words, that are all of the same length. Find all starting indices of substring(s) insthat is a conc...

Divide Two Integers MediumDivide two integers without using multiplication, division and mod operator.If it is overflow, return MAX_INT.public int divide(int dividend, int divisor) { if...

Implement strStr()EasyImplement strStr().Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.public int strStr(String haystack, String ne...

Remove Element EasyGiven 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 wit...

Remove Duplicates from Sorted Array EasyGiven a sorted array, remove the duplicates in place such that each element appear onlyonceand return the new length.Do not allocate extra space for an...

Reverse Nodes in k-Group HardGiven a linked list, reverse the nodes of a linked listkat a time and return its modified list.kis a positive integer and is less than or equal to the length of ...

Swap Nodes in Pairs MediumGiven a linked list, swap every two adjacent nodes and return its head.For example,Given1->2->3->4, you should return the list as2->1->4->3.Your...

Merge k Sorted Lists HardMergeksorted linked lists and return it as one sorted list. Analyze and describe its complexity.public ListNode mergeKLists(ListNode[] lists) { if (lists == nul...

Generate Parentheses MediumGivennpairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, givenn= 3, a solution set is:[ "((()))", ...

Merge Two Sorted Lists EasyMerge 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.public ListNode mergeTwo...

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

Remove Nth Node From End of List MediumGiven a linked list, remove thenthnode from the end of list and return its head.For example, Given linked list: 1->2->3->4->5, and n = ...

4Sum MediumGiven an arraySofnintegers, are there elementsa,b,c, anddinSsuch thata+b+c+d= target? Find all unique quadruplets in the array which gives the sum of target.Note:...

Letter Combinations of a Phone Number MediumGiven a digit string, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the telepho...

3Sum Closest MediumGiven an arraySofnintegers, find three integers inSsuch that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each ...

3Sum MediumGiven an arraySofnintegers, are there elementsa,b,cinSsuch thata+b+c= 0? Find all unique triplets in the array which gives the sum of zero.Note:The solution set must...

Longest Common Prefix EasyWrite a function to find the longest common prefix string amongst an array of strings.public String longestCommonPrefix(String[] strs) { if (strs.length == 0)...

Roman to Integer EasyGiven a roman numeral, convert it to an integer.Input is guaranteed to be within the range from 1 to 3999.public int romanToInt(String s) { int sum = 0; if (s....

Integer to Roman MediumRoman numerals are represented by seven different symbols:I,V,X,L,C,DandM.Symbol ValueI 1V 5X 10L 50...

Container With Most Water MediumGivennnon-negative integersa1,a2, ...,an, where each represents a point at coordinate (i,ai).nvertical lines are drawn such that the two endpoints of line...

Regular Expression Matching HardGiven an input string (s) and a pattern (p), implement regular expression matching with support for'.'and'*'.'.' Matches any single character.'*' Matches ze...

Palindrome Number EasyDetermine whether an integer is a palindrome. Do this without extra space.Some hints:Could negative integers be palindromes? (ie, -1)If you are thinking of converting ...

String to Integer (atoi) MediumImplementatoito 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 yours...

Reverse Integer EasyReverse 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 question...

ZigZag Conversion MediumThe 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...

Longest Palindromic Substring MediumGiven a strings, find the longest palindromic substring ins. You may assume that the maximum length ofsis 1000.Example:Input: "babad"Output: "bab"...

Median of Two Sorted Arrays HardThere are two sorted arraysnums1andnums2of size m and n respectively.Find the median of the two sorted arrays. The overall run time complexity should be O(lo...

Longest Substring Without Repeating Characters MediumGiven a string, find the length of thelongest substringwithout repeating characters.Examples:Given"abcabcbb", the answer is"abc", whic...

Add Two Numbers MediumYou are given twonon-emptylinked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add t...

Two sumGiven an array of integers, returnindicesof the two numbers such that they add up to a specific target.You may assume that each input would haveexactlyone solution, and you may not use ...