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comparison

所谓排序,就是使一串记录,按照其中的某个或某些关键字的大小,递增或递减的排列起来的操作。排序算法,就是如何使得记录按照要求排列的方法。排序算法在很多领域得到相当地重视,尤其是在大量数据的处理方面。一个优秀的算法可以节省大量的资源。在各个领域中考虑到数据的各种限制和规范,要得到一个符合实际的优秀算法,得经过大量的推理和分析。

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  • Comparison method violates its general contract!

    今天在刷LeetCode题目的时候,问题使用HashMap按照value排序来解决,自定义比较器,但是报错:java.lang.IllegalArgumentException: Comparison
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  • A simple performance comparison between CDS redirect and normal read

    Created by Wang, Jerry, last modified on Jan 05, 2017A very rough performance comparison is performedin ER9001.Comparison scenarioThe two below operations are compared:table ZCOMM_PRODUCT2This is a very
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  • ISO C forbids comparison between pointer and integer

    =0) s.pop_back();}异常:ISO C forbids comparison between pointer and integer 意思是:指针和整数比较出错;禁止指针和整数进行比较。
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  • 如何在此代码中使用PHP Comparison 和Ternary Operators?

    我一直在阅读文件(http:php.netmanualenlanguage.operators.comparison.php#language.operators.comparison.ternary
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  • 论文解读——Review and comparison of path tracking based on model……

    《Review and comparison of path tracking based on model predictive control》是期刊《Electronics》在2019年第8卷第10《Review and comparison of path tracking based on model predictive control》的主要写作目的,是为了澄清由于名称混乱而导致的研究者们对路径跟踪控制中越来越广泛使用的各种模型预测控制
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  • 6.1 关系操作符(Comparison Operators)

    ----6.1 关系操作符(Comparison Operators)关系操作符,用于比较同类型数据(不同类型的基础数据需要进行类型转换,不同长度的向量,不能进行比较)之间的大小关系或者等价关系。
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  • JDK7的Comparison method violates its general contract异常

    2.背景先说一下为什么要研究这个异常,前几天线上服务器发现日志里有偶发的异常:123456789java.lang.IllegalArgumentException: Comparison method看了一下源代码,抛出异常的那段源代码让人根本摸不着头脑:123if (len2 == 0) { throw new IllegalArgumentException(Comparison method
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  • ABAP Method remote comparison

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  • Comparison of Apache Stream Processing Frameworks: Part 2

    PerformanceReasonable performance comparison is definitely a topic for whole article.
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  • Overview of Kotlin & Comparison Between Kotlin and Java

    Reading Time: 10 Minutes by Navdeep Singh Gill ?imageWhat is Kotlin?Kotlin is a new programming language from JetBrains. It first appeared in 2011 when JetBrains unveiled their project named “Kotlin”. Kotlin is an Open-Source Language.Basically like Java, C and C++ - Kotlin is also “statically typed programming language”. Statically typed programming languages are those languages in which variables need not be defined before they are used. This means that static typing has to do with the explicit declaration or initialization of variables before they are employed.As Earlier said that Java is an example of a statically typed language, similarly C and C++ are also statically typed languages.Basically, Static typing does not mean that we have to declare all the variables first before we use them. Variables may be initialized anywhere in the program and we (developers) have to do so, to use those variables anywhere in the program when there is a need. Consider the following example?imageIn addition to the classes and methods of object-oriented programming, Kotlin also supports procedural programming with the use of functions.Like in Java, C and C++, the entry point to a Kotlin program is a function named “main”. Basically, it passed an array containing any command line arguments. Consider the following example -?imageFilename extensions of the Java are .java, .class, .jar but on the other hand filename extensions of the Kotlin are .kt and .kts.?imageBenefits of Kotlin LanguageKotlin compiles to JVM bytecode or JavaScript - Like Java, Bytecode is the compiled format for Kotlin programs also. Bytecode means Programming code that, once compiled, is run through a virtual machine instead of the computer’s processor. By using this approach, source code can be run on any platform once it has been compiled and run through the virtual machine. Once a kotlin program has been converted to bytecode, it can be transferred across a network and executed by JVM(Java Virtual Machine).Kotlin programs can use all existing Java Frameworks and Libraries - Yes, its true that Kotlin programs can use all existing java frameworks and libraries, even advanced frameworks that rely on annotation processing. The main important thing about kotlin language is that it can easily integrate with Maven, Gradle and other build systems.Kotlin can be learned easily and it is approachable. It can be learned easily by simply reading the language reference.The syntax is clean and intuitive(easy to use and understand). Kotlin looks a lot like Scala but is simpler.Kotlin is Open Source and it costs nothing to adopt.Automatic conversion of Java to Kotlin - JetBrains integrated a new feature into IntelliJ which converts Java to Kotlin and saves a huge amount of time. And it also saves us to retype mundane code.Kotlin’s null-safety is great - Now get rid of NullPointerExceptions. This type of system helps us to avoid null pointer exceptions. In Kotlin the system simply refuses to compile code that tries to assign or return null. Consider the following exampleval name: String = null tries to assign null, won’t compile. fun getName(): String = null tries to return null, won’t compile. Code reviews are not a problem - Kotlin is much more focuses on readable syntax so code reviews are not a problem, they can still be done by those team members who are not familiar with the language.Features of Kotlin LanguageThe billion dollar mistake made right. As already mentioned above that Kotlin avoids the null pointer exception. If we try to assign or return null to a variable or function respectively, then it won’t compile.But in some special cases if we need nullability in our program then we have to ask Kotlin very nicely. Every Nullable type require some special care and treatment. We can’t treat them the same way as non-nullable types and this is a very good thing.We have to add “?” after the variable type. Consider the following example - Kotlin also fails at compile-time whenever a NullPointerException may be thrown at run-time. Consider the following example -?imageVersatile?imageLean Syntax and Concise - One liner functions take one line, simple structsJavaBeans can also be declared in one line. Real properties generate getters and setters behind the scenes for Java interop. And Adding the data annotation to a class triggers autogeneration of boilerplate like equals, hashCode, toString and much more.Consider the following example* Java program *public class Address { private String street; private int streetNumber; private String postCode; private String city; private Country country; public Address(String street, int streetNumber, String postCode, String city, Country country) { this.street = street; this.streetNumber = streetNumber; this.postCode = postCode; this.city = city; this.country = country; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Address address = (Address) o; if (streetNumber != address.streetNumber) return false; if (!street.equals(address.street)) return false; if (!postCode.equals(address.postCode)) return false; if (!city.equals(address.city)) return false; return country == address.country; } @Override public int hashCode() { int result = street.hashCode(); result = 31 * result + streetNumber; result = 31 * result + postCode.hashCode(); result = 31 * result + city.hashCode(); result = 31 * result + (country != null ? country.hashCode() : 0); return result; } @Override public String toString() { return Address{ + street= + street + + , streetNumber= + streetNumber + , postCode= + postCode + + , city= + city + + , country= + country + }; } public String getStreet() { return street; } public void setStreet(String street) { this.street = street; } public int getStreetNumber() { return streetNumber; } public void setStreetNumber(int streetNumber) { this.streetNumber = streetNumber; } public String getPostCode() { return postCode; } public void setPostCode(String postCode) { this.postCode = postCode; } public String getCity() { return city; } public void setCity(String city) { this.city = city; } public Country getCountry() { return country; } public void setCountry(Country country) { this.country = country; }}?imageYou May Also Love To Read Deploying Kotlin Application on Docker & KubernetesCompilation Speed Java vs KotlinWe were actually very much interested in knowing the compilation speed of Kotlin as compared to Java.Difference Between Kotlin And Java?imageNull Safety - As already mentioned in above section that Kotlin avoids NullPointerException. Kotlin fails at compile-time whenever a NullPointerException may be thrown. Data Classes - In Kotlin there are Data Classes which leads to autogeneration of boilerplate like equals, hashCode, toString, getterssetters and much more. Consider the following example - ? image But in Kotlin the above same class can define concisely in one line* kotlin Code *data class Book(var title: Stri var author: Author)It will also allow us to easily make copies of data classes with the help of copy()?imageExtension Functions - Kotlin allows us to extend the functionality of existing classes without inheriting from them. Means to say that Kotlin provides the ability to extend a class with new functionality without having to inherit from the class. This is done by extension functions. To declare an extension function, we need to prefix its name with a receiver type, i.e. the type being extended. The following adds a swap function to MutableList?imageThe this keyword inside an extension function corresponds to the receiver object, the one that is passed before the dot. Now we can call such a function on any MutableList?imageSmart Casts - When it comes to casts, Kotlin compiler is really intelligent. In many cases, one does not need to use explicit cast operators in kotlin, but in Kotlin there is “is-checks” for immutable values and inserts casts automatically when needed?image Type Inference - In Kotlin, there is a great thing that you don’t have to specify the type of each variable explicitly(in clear and detailed manner). But if you want to define a data type explicitly, you can also do that. Consider the following example ? image Functional Programming - The main important thing is that Kotlin is a functional programming language. Basically Kotlin consist of many useful methods, which includes higher-order functions, lambda expressions, operator overloading, lazy evaluation, operator overloading and much more.Functional Programing makes Kotlin much more handier when it comes to collections?imageOutput - 15, 11Higher - Order Functionsare those functions that take functions as a parameter and also returns a function. Consider the following code:fun alphaNum(func: () -> Unit) {}In the above code “func” is the name of the parameter and “ ( ) -> Unit ” is the function type. In this case, we are saying that func will be a function that does not receive any parameter and does not return any value also.Lambda expression or an anonymous function is a “function literal”, i.e a function that is not declared, but passed immediately as an expression.Lambda ExpressionAn Example of a Lambda Expression?imageIn the above example, we simply declare a variable ‘sum’ that takes two integers and adds them together and returns total as an integer.Then we just use ‘ sum(2,2) ’ in order to call it. Pretty cool huh?Anonymous Function is a function which allows us to specify the return type and in this, the function name is omitted. Consider the following example:?image----Clean Builds Building your Codebase first timeWhen we compile our Kotlin code first time,then it takes more time than Java. Java compilation is almost around 15-20% faster than Kotlin.----Phases of Incremental BuildsBut as we know that Most of the time we need incremental builds like we are doing some modifications in our existing code and then building them and doing continuous deploymentSo in that perspective, Kotlin takes same amount of time to compile as compared to Java and even little bit faster than Java.----The Future of Kotlin languageKotlin interwork with Java and provdes incremental change of code and superior type system to Java and provides the easy Migration path from Java with backward compatability.With features Like more declarative, less code, mixed language database and more expressive than Java, Make Kotlin the future langauge for enterprises applications and Mobile.----Concluding Kotlin vs JavaWe know that clean build is done only one time in our project and I think Incremental Builds Compilation time are more crucial for us than Clean Build. So Kotlin is almost same as Java and yes we can go with Kotlin without worrying about Compilation time.
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  • A Comparison Between Spring and Spring Boot

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  • Comparison method violates its general contract!

    背景16号为了统一线上服务器运行环境,将两台服务器的Tomcat6+JDK6升级到Tomcat7+JDK7,本以为很简单的事情,升级后自己验证也没问题,没想到却悲剧了。升级后,过了半小时运营就找过来反馈问题,部分角色无法登陆系统,由于异常日志没有输出,没有找到问题,无奈回滚。今天我们就来说说JDK6升级到JDK7会遇到的坑。本文为了方便搜索,就直接以异常信息作为文章标题了。复现回滚后,到beta环境按照线上的权限配置,复现该问题,加上了error日志输出,输出了文章标题的异常,这个异常是在类似如下代码中抛出的:Collections.sort(list, new Comparator() { @Override public int compare(Integer o1, Integer o2) { return o1 > o2 ? 1 : -1; 错误的方式 }});解决方案先说如何解决,解决方式有两种。修改代码上面代码写的本身就有问题,第4行没有考虑o1 == o2的情况,再者说我们不需要自己去比较,修改为如下代码即可:Collections.sort(list, new Comparator() { @Override public int compare(Integer o1, Integer o2) { return o1 > o2 ? 1 : -1; return o1.compareTo(o2); 正确的方式 }});不修改代码那么问题来了。为什么上面代码在JDK6中运行无问题,而在JDK7中却会抛异常呢?这是因为JDK7底层的排序算法换了,如果要继续使用JDK6的排序算法,可以在JVM的启动参数中加入如下参数:-Djava.util.Arrays.useLegacyMergeSort=true这样就会照旧使用JDK6的排序算法,在不能修改代码的情况下,解决这个兼容的问题。分析在我以前的认知中,高版本的JDK是可以兼容之前的代码的,与同事讨论了一番另加搜索了一番,事实证明,JDK6到JDK7确实存在兼容问题(不兼容列表)。在不兼容列表中我们可以找到关于Collections.sort的不兼容说明,如下:Area: API: UtilitiesSynopsis: Updated sort behavior for Arrays and Collections may throw an IllegalArgumentExceptionDescription: The sorting algorithm used by java.util.Arrays.sort and (indirectly) by java.util.Collections.sort has been replaced. The new sort implementation may throw an IllegalArgumentException if it detects a Comparable that violates the Comparable contract. The previous implementation silently ignored such a situation.If the previous behavior is desired, you can use the new system property, java.util.Arrays.useLegacyMergeSort, to restore previous mergesort behavior.Nature of Incompatibility: behavioralRFE: 6804124描述的意思是说,java.util.Arrays.sort(java.util.Collections.sort调用的也是此方法)方法中的排序算法在JDK7中已经被替换了。如果违法了比较的约束新的排序算法也许会抛出llegalArgumentException异常。JDK6中的实现则忽略了这种情况。那么比较的约束是什么呢?看这里,大体如下: ?sgn(compare(x, y)) == -sgn(compare(y, x)) ((compare(x, y)>0) && (compare(y, z)>0)) implies compare(x, z)>0 compare(x, y)==0 implies that sgn(compare(x, z))==sgn(compare(y, z)) for all z再回过头来看我们开篇有问题的实现:return x > y ? 1 : -1; 当x == y时,sgn(compare(x, y))  = -1,-sgn(compare(y, x)) = 1,这违背了sgn(compare(x, y)) == -sgn(compare(y, x))约束,所以在JDK7中抛出了本文标题的异常。结论那么现在是否可以盖棺定论了,按照上面的分析来看,使用这种比较方式(return x > y ? 1 : -1;),只要集合或数组中有相同的元素,就会抛出本文标题的异常。实则不然,什么情况下抛出异常,还取决于JDK7底层排序算法的实现,也就是大名鼎鼎的TimSort。后面文章会分析TimSort。本文给出一个会引发该异常的Case,以便有心人共同研究,如下:Integer[] array = {0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 2, 1, 0, 0, 0, 2, 30, 0, 3};      (完)
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  • sparklines迷你图系列6——Comparison(Columns)

    今天分享sparklines迷你图中的Comparision图表类型中的Columns图表。该图表说到底其实就是我们日常工作中最常用到的柱形图。该图表的函数参数较多,一共有15个之多,但是很多元素并不适合同时出现,这里一般我们会用到的有效参数也就五六个左右。关于每一个参数的具体含义以及在图表中所控制的图表元素,以上图示中已经演示的很清晰了, 需要注意的是,红色参数是必备参数(不可缺),其他的参数都是可选参数或者具有默认值的参数。?????为了图表的整体美观性,这会重点提示几个参数:points:这个是必备参数,是指标输入单元格区域;Mini,Maxi:最小值、最大值边界,也就是该图表的纵坐标轴范围。Line1,Line2:这两个是高低值的对比参考线,用于比较参照,没有实际意义。ColorPositive,ColorPositive:正负值显示的填充颜色,这两个参数最好还是设置一下,设置成项目的对比色,便于通过颜色进行区分。其他的参数个人感觉实际意义不大,感兴趣可以自己探索下。下面是Excel中函数菜单输入:??同样通过函数公式填充,可以批量做图,形成一组迷你图报告。 ??
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