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Aboomerangis a set of 3 points that are all distinct andnotin a straight line.Given a listof three points in the plane, return whether these points are a boomerang.Example 1:Input: [[1...

Every non-negative integerNhas a binary representation. For example,5can be represented as"101"in binary,11as"1011"in binary, and so on. Note that except forN = 0, there are no leading z...

Find thenthdigit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...Note:nis positive and will fit within the range of a 32-bit signed integer (n< 231).Example 1:Inp...

Given an arrayAof integers, wemustmodify the array in the following way: we choose aniand replaceA[i]with-A[i], and we repeat this processKtimes in total. (We may choose the same indexi...

We are given that the string"abc"is valid.From any valid stringV, we may splitVinto two piecesXandYsuch thatX + Y(Xconcatenated withY) is equal toV. (XorYmay be empty.) Then,X + ...

Given an arrayAof strings made only from lowercase letters, return a list of all characters that show up in all strings within the list(including duplicates).For example, if a character occurs 3...

题目来源：https://leetcode.com/explore/learn/card/queue-stack/228/first-in-first-out-data-structure/1337/class MyCircularQueue { int[] circularQueue = null; int headPos, rearPos = -1, amount; ...

In a town, there are N people labelled from 1 to N.  There is a rumor that one of these people is secretly the town judge.If the town judge exists, then:The town judge trusts nobody. Everybody (...

Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters.This is case sensitive, for example "Aa" is not cons...

A binary watch has 4 LEDs on the top which represent the hours (0-11), and the 6 LEDs on the bottom represent the minutes (0-59).Each LED represents a zero or one, with the least significant bit on...

In a list of songs, thei-thsong has a duration oftime[i]seconds.Return the number of pairs of songs for which their totalduration in seconds is divisible by60. Formally, we want the number ...

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree[1,2,2,3,4,4,3]is symmetric: 1 / \ 2 2 / \ / \3 4 4 3...

A valid parentheses string is either empty(""),"(" + A + ")", orA + B, whereAandBare valid parentheses strings, and+represents string concatenation. For example,"","()","(())()", and"(()...

Given a numberN, return a string consisting of"0"s and"1"sthat represents its value in base-2(negative two).The returned string must have no leading zeroes, unless the string is"0".Exam...

We are given a linked list withheadas the first node. Let's number thenodes in the list:node_1, node_2, node_3, ...etc.Each node may have anext largervalue: fornode_i,next_larger(node_i)...

Given an arrayAof0s and1s, considerN_i: the i-th subarray fromA[0]toA[i]interpretedas a binary number (from most-significant-bit to least-significant-bit.)Return a list of booleansanswer...

Given a binary stringS(a string consisting only of '0' and '1's) and a positive integerN, return true if and only if for every integer X from 1 to N, the binary representation of X is a substring ...

Given a binary tree, flatten it to a linked list in-place.For example, given the following tree: 1 / \ 2 5 / \ \3 4 6The flattened tree should look like:1 \ 2 \ ...

Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.Note:The given integer is guaranteed to fit within the range of a ...

Given a linked list, determine if it has a cycle in it.To represent a cycle in the given linked list, we use an integerposwhich represents the position (0-indexed)in the linked list where tail c...

Given a stringsand anon-emptystringp, find all the start indices ofp's anagrams ins.Strings consists of lowercase English letters only and the length of both stringssandpwill not be larg...

In a binary tree, the root node is at depth 0, and children of each depth k node are at depth k+1.Two nodes of a binary tree are cousins if they have the same depth, but have different parents.We...

The Hamming distance between two integers is the number of positions at which the corresponding bits are different.Given two integers x and y, calculate the Hamming distance.Note:0 ≤ x, y < 2...

Two main scenarios of using BFS: do traversal or find the shortest path. Typically, it happens in a tree or a graph.In some cases, we can abstract a specific question into a tree or a graph. The nod...

A subarray A[i], A[i+1], ..., A[j] of A is said to be turbulent if and only if:For i <= k < j, A[k] > A[k+1] when k is odd, and A[k] < A[k+1] when k is even; OR, for i <= k < j, ...

辗转相除法基于如下原理：两个整数的最大公约数等于其中较小的数和两数的相除余数的最大公约数。 to complete

Given an array A of positive lengths, return the largest perimeter of a triangle with non-zero area, formed from 3 of these lengths.If it is impossible to form any triangle of non-zero area, return...

We have a list of points on the plane.  Find the K closest points to the origin (0, 0).(Here, the distance between two points on a plane is the Euclidean distance.)You may return the answer in an...

Given a positive integer N, how many ways can we write it as a sum of consecutive positive integers?Example 1:Input: 5Output: 2Explanation: 5 = 5 = 2 + 3Example 2:Input: 9Output: 3Expla...

S and T are strings composed of lowercase letters. In S, no letter occurs more than once.S was sorted in some custom order previously. We want to permute the characters of T so that they match the ...

这个文章是几年前水acm的时候转的, 当时也不知道作者是谁, 要是有人知道的话说一下吧并查集是我暑假从高手那里学到的一招，觉得真是太精妙的设计了。以前我无法解决的一类问题竟然可以用如此简单高效的方法搞定。不分享出来真是对不起party了。（party：我靠，关我嘛事啊？我跟你很熟么？）来看一个实例，杭电1232畅通工程...

一，常见排序算法排序算法 是否稳定 时间复杂度 空间复杂度   冒泡排序         插入排序         选择排序         快速排序         基数排序         希尔排序     ...

结点类 private static class TreeNode { private int value; TreeNode left, right; public TreeNode(int value) { this.value = value; } }   构建二叉树 ...

Given an array of integers A sorted in non-decreasing order, return an array of the squares of each number, also in sorted non-decreasing order. Example 1:Input: [-4,-1,0,3,10]Output: [0,1,9,...

todo

We have an array A of integers, and an array queries of queries.For the i-th query val = queries[i][0], index = queries[i][1], we add val to A[index].  Then, the answer to the i-th query is the sum...

Related tops: DFS & RecursionGiven 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 given sum.Note: A leaf i...

贪心算法Given two integers A and B, return any string S such that:S has length A + B and contains exactly A 'a' letters, and exactly B 'b'letters; The substring 'aaa' does not occur in S; The subst...

Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), ..., (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as pos...

backtracking + dfs + recursive 784. Letter Case PermutationEasy49661FavoriteShareGiven a string S, we can transform every letter individually to be lowercase or uppercase to create another st...