wuqingdeqing的博客

Given two strings s and t, determine if they are isomorphic.Two strings are isomorphic if the characters in s can be replaced to get t.All occurrences of a character must be replaced with another character while preserving the order of characters. No two

SQL SchemaWrite a SQL query to find all duplicate emails in a table named Person.±—±--------+| Id | Email |±—±--------+| 1 | a@b.com || 2 | c@d.com || 3 | a@b.com |±—±--------+For example, your query should return the following for the above

Given an integer n, return the number of trailing zeroes in n!.Follow up: Could you write a solution that works in logarithmic time complexity?Example 1:Input: n = 3Output: 0Explanation: 3! = 6, no trailing zero.Example 2:Input: n = 5Output: 1Expl

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.You may assume that the array is non-empty and the majority element always exist in the array.Example 1:Input: [3,2,3]Output:

Given an array of integers that is alreadysorted in ascending order, find two numbers such that they add up to a specific target number.The function twoSum should return indices of the two numbers ...

153.Find Minimum in Rotated Sorted ArrayMedium1413192FavoriteShareSuppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.(i.e., [0,1,2,4,5,6,7]might b...

Given an input string, reverse the string word by word.Example 1:Input: "the sky is blue"Output:"blue is sky the"Example 2:Input: " hello world! "Output:"world! hello"Explanation:...

Given a binary tree, return thepreordertraversal of its nodes' values.Example:Input:[1,null,2,3] 1 \ 2 / 3Output:[1,2,3]Follow up:Recursive solution is trivial, could...

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 co...

Given 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 the following triangle[ [2], [3,4], [6,5...

Determine whether an integer is a palindrome. An integerisapalindrome when itreads the same backward as forward.Example 1:Input: 121Output: trueExample 2:Input: -121Output: falseExpl...

Given the root node of a binary search tree (BST) and a value. You need to find the node in the BST that the node's value equals the given value. Return the subtree rooted with that node. If such node...

There is a robot starting at position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robotends up at (0, 0)after it completes its moves.The move sequence is represe...

Given an arrayAof non-negative integers, return an array consisting of all the even elements ofA, followed by all the odd elements ofA.You may return any answer array that satisfies this conditi...

You are given annxn2D matrix representing an image.Rotate the image by 90 degrees (clockwise).Note:You have to rotate the imagein-place, which means you have to modify the input 2D matrix d...

Implement function ToLowerCase() that has a string parameter str, and returns the same string in lowercase. Example 1:Input: "Hello"Output: "hello"Example 2:Input: "here"Output: "here"...

Given a string, find the length of thelongest substringwithout repeating characters.Example 1:Input: "abcabcbb"Output: 3 Explanation: The answer is "abc", with the length of 3. Example 2:...

Given 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 thesame...

Given a linked list, remove then-th node from the end of list and return its head.Example:Given linked list: 1->2->3->4->5, and n = 2.After removing the second node from the end, t...

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.You may assume no duplicates in the array....

Given an arraynumsand a valueval, remove all instances of that valuein-placeand return the new length.Do not allocate extra space for another array, you must do this bymodifying the input arra...

Write an efficient algorithm that searches for a value in anmxnmatrix. This matrix has the following properties:Integers in each row are sorted from left to right. The first integer of each row...

Given a sorted linked list, delete all duplicates such that each element appear onlyonce.Example 1:Input: 1->1->2Output: 1->2Example 2:Input: 1->1->2->3->3Output: 1-...

6.1 API优先队列是一种抽象数据类型，它表示了一组值和对这些值的操作。优先队列最重要的操作就是删除最大元素和插入元素。6.2 初级实现6.2.1 数组实现（无序）或许实现优先队列最简单方法就是基于下压栈的代码。insert()方法的代码和栈的完全一样。要实现删除最大元素，可以添加一段类似选择排序的内循环的代码，将最大元素和边界元素交换然后删除它，和栈的pop()方法的实现一样。和栈类似，也可以...

Every email consists of a local name and a domain name, separated by the @ sign.For example, in alice@leetcode.com, alice is the local name, and leetcode.com is the domain name.Besides lowercase l...

You are playing a simplified Pacman game. You start at the point (0, 0), and your destination is (target[0], target[1]). There are several ghosts on the map, the i-th ghost starts at (ghosts[i][0], gh...

You're given strings J representing the types of stones that are jewels, and S representing the stones you have.  Each character in Sis a type of stone you have.  You want to know how many of the ston...

Write an algorithm to determine if a number is "happy".A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares o...

Given a list of sorted characters letters containing only lowercase letters, and given a target letter target, find the smallest element in the list that is larger than the given target.Letters also...

Given an array containing n distinct numbers taken from 0, 1, 2, ..., n, find the one that is missing from the array.Example 1:Input: [3,0,1]Output: 2Example 2:Input: [9,6,4,2,3,5,7,0,1]O...

Given an unsorted array of integers, find the length of longest continuous increasing subsequence (subarray).Example 1:Input: [1,3,5,4,7]Output: 3Explanation: The longest continuous increasing ...

We are given two strings, A and B.A shift on A consists of taking string A and moving the leftmost character to the rightmost position. For example, if A = 'abcde', then it will be 'bcdea' after one...

要将一个数组排序，可以先将它分成两半分别排序，然后将结果归并起来。这就是归并排序。归并排序的主要优势是它能保证将任意长度为n的数组排序所需时间与nlogn成正比，它的主要缺点则是它所需的额外空间与n成正比。4.1 原地归并原地排序先将前半部分排序，再将后半部分排序，然后在数组中移动元素而不需要使用额外的空间。public static void merge(Comparable[] a, int ...

希尔排序是一种快速的基于插入排序的排序算法。对于大规模乱序数组插入排序很慢，因为它只会交换相邻的元素，因此元素只能一点一点从数组的一端移动到另一端。希尔排序为了加快速度简单改进了插入排序，交换不相邻的元素以对数组的局部进行排序，并最终用插入排序将局部有序的数组排序。希尔排序的思想是使数组中任意间隔为h的元素都是有序的。这样的数组被称为h有序数组。即一个h有序数组就是h个互相独立的有序数组编织在一起...

快速排序可能是应用最广泛的排序算法。快速排序流行的原因是因为它实现简单、适用于各种不同的输入数据且在一般应用中比其他排序算法都要快的多。快速排序的特点包括它是原地排序（只需要一个很小的辅助栈），且将长度为n的数组排序所需的时间和nlogn成正比。快速排序的内循环比大多数排序算法都要短小，这意味着无论是理论上还是实际上都要更快。它的主要缺点是非常脆弱，在实现时要非常小心才能避免低劣的性能，许多错误都...

今日刷到LeetCode766题，判断给定的矩阵是否托普利兹矩阵。托普利兹矩阵，简称为T型矩阵。托普利兹矩阵的主对角线上的元素相等，平行于主对角线的线上的元素也相等；矩阵中的各元素关于次对角线对称，即T型矩阵为次对称矩阵。本人所写代码如下：class Solution { public boolean isToeplitzMatrix(int[][] matrix) { ...

与选择排序一样，当前索引左边的所有元素都是有序的，但它们的最终位置还不确定，为了给更小的元素腾出空间，它们可能会被移动。当索引到达数组右端时，数组排序就完成了。和选择排序不同的是，插入排序所需的时间取决于输入元素的初始位置。例如，对一个很大且其中的元素已经有序的数组进行排序将会比对随机顺序的数组或是逆序数组进行排序要快得多。对于随机排列的长度为N且主键不重复的数组，平均情况下插入排序需要~(N^2...

Given an integer array, find three numbers whose product is maximum and output the maximum product.Example 1:Input: [1,2,3]Output: 6 Example 2:Input: [1,2,3,4]Output: 24 Note:The...

You are given a string representing an attendance record for a student. The record only contains the following three characters: 'A' : Absent. 'L' : Late. 'P' : Present. A student could be re...

Given a string S of '(' and ')' parentheses, we add the minimum number of parentheses ( '(' or ')', and in any positions ) so that the resulting parentheses string is valid.Formally, a parentheses s...