摘要：Climbing StairsYou are climbing a stair case. It takesnsteps to reach to the top.Each time you can either climb 1 or 2 steps. In how many distinct way...
阅读全文
摘要：Longest Substring Without Repeating CharactersGiven a string, find the length of the longest substring without repeating characters. For example, the ...
阅读全文
摘要：Longest Common PrefixWrite a function to find the longest common prefix string amongst an array of strings.算法思路：思路：貌似木有什么捷径，逐个比较，遇到不同即断开。代码如下： 1 publi...
阅读全文
摘要：Populating Next Right Pointers in Each Node IIFollow up for problem "Populating Next Right Pointers in Each Node".What if the given tree could be any ...
阅读全文
摘要：Populating Next Right Pointers in Each NodeGiven a binary tree struct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLi...
阅读全文
摘要：Path Sum IIGiven a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.For example:Given the below binary tr...
阅读全文
摘要：Path SumGiven a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the give...
阅读全文
摘要：Balanced Binary TreeGiven a binary tree, determine if it is height-balanced.For this problem, a height-balanced binary tree is defined as a binary tre...
阅读全文
摘要：Convert Sorted Array to Binary Search TreeGiven an array where elements are sorted in ascending order, convert it to a height balanced BST.算法：根据有序数组，生...
阅读全文
摘要：Construct Binary Tree from Inorder and Postorder TraversalGiven inorder and postorder traversal of a tree, construct the binary tree.Note:You may assu...
阅读全文
摘要：Construct Binary Tree from Preorder and Inorder TraversalGiven preorder and inorder traversal of a tree, construct the binary tree.Note:You may assume...
阅读全文
摘要：Minimum Depth of Binary TreeGiven a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root...
阅读全文
摘要：Maximum Depth of Binary TreeGiven a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root ...
阅读全文
摘要：Same TreeGiven two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally ide...
阅读全文
摘要：Symmetric TreeGiven a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric...
阅读全文
摘要：Recover Binary Search TreeTwo elements of a binary search tree (BST) are swapped by mistake.Recover the tree without changing its structure.Note:A sol...
阅读全文
摘要：Validate Binary Search TreeGiven a binary tree, determine if it is a valid binary search tree (BST).Assume a BST is defined as follows:The left subtre...
阅读全文
摘要：Pow(x, n)Implement pow(x,n).算法思路：二分法，没什么好说的，小心点就行；这个题时间比较苛刻。return pow(x,n >> 1) * pow(x,n >> 1) 是过不去的，因此把pow(x,n / 2)求出来先。其实时间复杂度而言，是一样的。【注意】：n的取值范围；...
阅读全文
摘要：Subsets IIGiven a collection of integers that might contain duplicates,S, return all possible subsets.Note:Elements in a subset must be in non-descend...
阅读全文
摘要：SubsetsGiven a set of distinct integers,S, return all possible subsets.Note:Elements in a subset must be in non-descending order.The solution set must...
阅读全文
摘要：Insert IntervalGiven a set ofnon-overlappingintervals, insert a new interval into the intervals (merge if necessary).You may assume that the intervals...
阅读全文
摘要：Merge IntervalsGiven a collection of intervals, merge all overlapping intervals.For example,Given[1,3],[2,6],[8,10],[15,18],return[1,6],[8,10],[15,18]...
阅读全文
摘要：Valid PalindromeGiven a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.For example,"A man, a pla...
阅读全文
摘要：Merge Sorted ArrayGiven two sorted integer arrays A and B, merge B into A as one sorted array.Note:You may assume that A has enough space (size that i...
阅读全文
摘要：Length of Last WordGiven a stringsconsists of upper/lower-case alphabets and empty space characters' ', return the length of last word in the string.I...
阅读全文
摘要：Simplify PathGiven an absolute path for a file (Unix-style), simplify it.For example,path="/home/", =>"/home"path="/a/./b/../../c/", =>"/c"click to sh...
阅读全文
摘要：Add BinaryGiven two binary strings, return their sum (also a binary string).For example,a ="11"b ="1"Return"100".算法思路：模拟二进制加法，跟十进制木有区别，将a，b转置(不转置的话，倒着...
阅读全文
摘要：Substring with Concatenation of All WordsYou are given a string,S, and a list of words,L, that are all of the same length. Find all starting indices o...
阅读全文
摘要：Valid ParenthesesGiven a string containing just the characters'(',')','{','}','['and']', determine if the input string is valid.The brackets must clos...
阅读全文
摘要：Reverse Words in a StringGiven an input string, reverse the string word by word.For example,Given s = "the sky is blue",return "blue is sky the".click...
阅读全文
摘要：ZigZag ConversionThe string"PAYPALISHIRING"is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern i...
阅读全文
摘要：Gray CodeThe gray code is a binary numeral system where two successive values differ in only one bit.Given a non-negative integernrepresenting the tot...
阅读全文
摘要：Permutation SequenceThe set[1,2,3,…,n]contains a total ofn! unique permutations.By listing and labeling all of the permutations in order,We get the fo...
阅读全文
摘要：Next PermutationImplement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.If such arrangemen...
阅读全文
摘要：Permutations IIGiven a collection of numbers that might contain duplicates, return all possible unique permutations.For example,[1,1,2]have the follow...
阅读全文
摘要：Add Two NumbersYou are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes co...
阅读全文
摘要：PermutationsGiven a collection of numbers, return all possible permutations.For example,[1,2,3]have the following permutations:[1,2,3],[1,3,2],[2,1,3]...
阅读全文
摘要：CombinationsGiven two integersnandk, return all possible combinations ofknumbers out of 1 ...n.For example,Ifn= 4 andk= 2, a solution is:[ [2,4], [3...
阅读全文
摘要：TriangleGiven a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.For example, given...
阅读全文
摘要：Pascal's Triangle IIGiven an indexk, return thekthrow of the Pascal's triangle.For example, givenk= 3,Return[1,3,3,1].Note:Could you optimize your alg...
阅读全文
摘要：Pascal's TriangleGivennumRows, generate the firstnumRowsof Pascal's triangle.For example, givennumRows= 5,Return[ [1], [1,1], [1,2,1], [1,3,...
阅读全文
摘要：Remove Duplicates from Sorted Array IIFollow up for "Remove Duplicates":What if duplicates are allowed at mosttwice?For example,Given sorted array A =...
阅读全文
摘要：Remove Duplicates from Sorted ArrayGiven a sorted array, remove the duplicates in place such that each element appear onlyonceand return the new lengt...
阅读全文
摘要：Remove ElementGiven 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. ...
阅读全文
摘要：Sort ListSort a linked list inO(nlogn) time using constant space complexity.算法思想：时间复杂度为O(nlogn)的排序算法，有快排、归并、堆排序，快排需要往前遍历，因此不适合单链表，堆排序可以，但是需要O(n)的空间，因此...
阅读全文
摘要：Reverse Linked List IIReverse a linked list from positionmton. Do it in-place and in one-pass.For example:Given1->2->3->4->5->NULL,m= 2 andn= 4,return...
阅读全文
摘要：Reverse Nodes in k-GroupGiven a linked list, reverse the nodes of a linked listkat a time and return its modified list.If the number of nodes is not a...
阅读全文
摘要：Reorder ListGiven a singly linked listL:L0→L1→…→Ln-1→Ln,reorder it to:L0→Ln→L1→Ln-1→L2→Ln-2→…You must do this in-place without altering the nodes' val...
阅读全文
摘要：Insertion Sort ListSort a linked list using insertion sort.算法思路：最基本的插入排序，时间复杂度O(n*n)，空间复杂度O(1)代码： 1 public class Solution { 2 public ListNode inse...
阅读全文
摘要：Partition ListGiven a linked list and a valuex, partition it such that all nodes less thanxcome before nodes greater than or equal tox.You should pres...
阅读全文
摘要：Remove Duplicates from Sorted List IIGiven a sorted linked list, delete all nodes that have duplicate numbers, leaving onlydistinctnumbers from the or...
阅读全文
摘要：Remove Duplicates from Sorted ListGiven a sorted linked list, delete all duplicates such that each element appear onlyonce.For example,Given1->1->2, r...
阅读全文
摘要：Merge k Sorted ListsMergeksorted linked lists and return it as one sorted list. Analyze and describe its complexity.这道题，第一次刷是过了，第二次同样的代码超时了，看来case是在不断...
阅读全文
摘要：Merge Two Sorted ListsMerge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the fir...
阅读全文
摘要：Rotate ListGiven a list, rotate the list to the right bykplaces, wherekis non-negative.For example:Given1->2->3->4->5->NULLandk=2,return4->5->1->2->3-...
阅读全文
摘要：Swap Nodes in PairsGiven a linked list, swap every two adjacent nodes and return its head.For example,Given1->2->3->4, you should return the list as2-...
阅读全文
摘要：Remove Nth Node From End of ListGiven a linked list, remove thenthnode from the end of list and return its head.For example, Given linked list: 1->2...
阅读全文
摘要：Linked List Cycle IIGiven a linked list, return the node where the cycle begins. If there is no cycle, returnnull.Follow up:Can you solve it without u...
阅读全文
摘要：Linked List CycleGiven a linked list, determine if it has a cycle in it.Follow up:Can you solve it without using extra space?算法思路1：快慢指针，当两个指针相遇，则表示有环，...
阅读全文
摘要：Palindrome NumberDetermine whether an integer is a palindrome. Do this without extra space.click to show spoilers.Some hints:Could negative integers b...
阅读全文
摘要：这篇博文较长，且理论为主，因为我准备换种风格，以保证大家看的时候不会觉得无聊，看完如果对dfs还是一头雾水，那我也不会请你吃麻辣烫开场:刷了一遍leetcode，发现DFS是个特别强大，且出题率特别高的一个基础算法，第一次接触DFS是树的一个搜索算法，相对而言的是BFS。根据难度与考察频率参考表的建...
阅读全文
摘要：Reverse IntegerReverse digits of an integer.Example1:x = 123, return 321Example2:x = -123, return -321click to show spoilers.Have you thought about th...
阅读全文
摘要：Plus OneGiven a non-negative number represented as an array of digits, plus one to the number.The digits are stored such that the most significant dig...
阅读全文
摘要：Set Matrix ZeroesGiven amxnmatrix, if an element is 0, set its entire row and column to 0. Do it in place.Follow up:Did you use extra space?A straight...
阅读全文
摘要：Validate Binary Search TreeRecover Binary Search TreeSymmetric TreeSame TreeMaximum Depth of Binary TreeConstruct Binary Tree from Preorder and Inorde...
阅读全文
摘要：Count and SayThe count-and-say sequence is the sequence of integers beginning as follows:1, 11, 21, 1211, 111221, ...1is read off as"one 1"or11.11is r...
阅读全文
摘要：Palindrome PartitioningGiven a strings, partitionssuch that every substring of the partition is a palindrome.Return all possible palindrome partitioni...
阅读全文
摘要：Letter Combinations of a Phone NumberGiven a digit string, return all possible letter combinations that the number could represent.A mapping of digit ...
阅读全文
摘要：Restore IP AddressesGiven a string containing only digits, restore it by returning all possible valid IP address combinations.For example:Given"255255...
阅读全文
摘要：Generate ParenthesesGivennpairs of parentheses, write a function to generate all combinations of well-formed parentheses.For example, givenn= 3, a sol...
阅读全文
摘要：Word SearchGiven a 2D board and a word, find if the word exists in the grid.The word can be constructed from letters of sequentially adjacent cell, wh...
阅读全文
摘要：N-Queens IIFollow up for N-Queens problem.Now, instead outputting board configurations, return the total number of distinct solutions.算法思路：与[leetcode]...
阅读全文
摘要：N-QueensThen-queens puzzle is the problem of placingnqueens on ann×nchessboard such that no two queens attack each other.Given an integern, return all...
阅读全文
摘要：Combination SumGiven a set of candidate numbers (C) and a target number (T), find all unique combinations inCwhere the candidate numbers sums toT.Thes...
阅读全文
摘要：Combination Sum IIGiven a collection of candidate numbers (C) and a target number (T), find all unique combinations inCwhere the candidate numbers sum...
阅读全文
摘要：本文载自【k sum problem】以及【NSum】有位同僚，对该问题做出了代码的小结，想看吗？戳我戳我。问题陈述：在一个数组，从中找出k个数（每个数不能重复取。数组中同一个值有多个，可以取多个），使得和为零。找出所有这样的组合，要求没有重复项（只要值不同即可，不要求在原数组中的index不同）解...
阅读全文
摘要：4SumGiven an arraySofnintegers, are there elementsa,b,c, anddinSsuch thata+b+c+d= target? Find all unique quadruplets in the array which gives the sum...
阅读全文
摘要：3Sum ClosestGiven an arraySofnintegers, find three integers inSsuch that the sum is closest to a given number, target. Return the sum of the three int...
阅读全文
摘要：3SumGiven 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:El...
阅读全文
摘要：Two SumGiven 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...
阅读全文
