删除在链表中出现多次的每个元素的第一个匹配项

Question

编写方法removeFirst，类LinkedList的成员，它删除列表中出现多次的每个元素的第一个匹配项。不要使用任何辅助数据结构，也不要调用任何方法。方法签名是public void removeFirst（）。

例4.1。如果列表包含：B =＆gt; A =＆gt; A =＆gt; R =＆gt; C =＆gt; A =＆gt; C =＆gt;那么R 在调用removeFirst之后，其内容变为B =＆gt; A =＆gt; A =＆gt; C =＆gt; R上。

我作为Arraylist类的成员解决了它，我使用了辅助数据结构。

public void removeFirst() {

Node<T> traverse = head;

        int[] array = new int[10];
        int[] repeat = new int[10];
        int count=0;
        int rcount=0;

        boolean isAlready = false;

        while (traverse!=null)
        {
            for (int i=0; i<count; i++)
            {
                if (array[i]==traverse.value)
                {
                    isAlready=true;
                    break;
                }
            }

            if(!isAlready)
                array[count++] = traverse.value;
            else
                repeat[rcount++] = traverse.value;

            traverse = traverse.next;
        }

        traverse= head;
        while (traverse!=null)
        {
            for (int i=0; i<rcount; i++)

            traverse=traverse.next;
        }

    }//

任何想法如何在不使用任何辅助数据结构的情况下作为likeslist类的成员来解决，你可以使用的是

public class Node<T> {
public T data;
public Node<T> next;
public Node () {
data = null;
next = null;
}
public Node (T val) {
data = val;
next = null;
}
// Setters/Getters...
}//End of class Node

public class LinkedList<T> { //LinkedList class
private Node<T> head;
private Node<T> current;
public LinkedList () {
head = current = null;
}

Answer 1

我在学习数据结构课程时遇到了这个问题，虽然有点困难，但这是我所做的。

public void removeFirst() {
    int counter = 0 ;
    Node<T> tmp = null ; 
    Node<T> comp = head ; 
    current = head ;
    Node<T> secHead = null ;
    Node<T> secCurr = null ; 
    boolean check = false ;
    boolean control = true ;
    while(current.next != null || current == null) {
        counter = 0 ; 
        comp = head ;
        while(comp.next != null) { // we iterate using node through original list to check for occurences 
            if(comp.data == current.data) {
                counter++;
            }

            comp = comp.next ; 
        }
        if(comp.data == current.data) {
            counter++;
        }
        tmp = current ;
        if(counter >= 2) { 
            check = false ;
            secCurr = secHead ;
            while(secCurr != null) { // check for deleting to avoid multiple deletes  

                if(tmp.data.equals(secCurr.data)) {
                    check = true ;
                    break ;
                }
                secCurr = secCurr.next ;
            }
            secCurr = secHead ;
            if(!check) { // deleting and adding to our secondary linkedlist to check it later :)
                remove();
                control = false ;
                Node<T> tmp2;
                if (secHead == null) {
                    secHead = new Node<T> (tmp.data);
                    secCurr = secHead ;
                }
                else {
                    tmp2 = secCurr.next;
                    secCurr.next = new Node<T> (tmp.data);
                    secCurr = secCurr.next;
                    secCurr.next = tmp2;
                }
            }


        }
        if(control) { // remove() increment the current this is for checking 
            current = current.next ;
        }
        control = true ;

    }
}

通过使用类节点的属性，您可以创建辅助LinkedList，但不使用类本身，因此我们从未使用辅助数据结构。您需要了解内部方法的具体工作方式。仔细阅读代码：）

Answer 2

2016-05-13 08:45:32.531 ERROR 19581 --- [           main] o.s.boot.SpringApplication               : Application startup failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration$InfoPropertiesConfiguration': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private final org.springframework.core.env.ConfigurableEnvironment org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration$InfoPropertiesConfiguration.environment; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.core.env.ConfigurableEnvironment] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1210)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:118)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:686)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:320)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:957)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:946)
    at com.bettercloud.synchronizer.Application.main(Application.java:14)
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration$InfoPropertiesConfiguration': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private final org.springframework.core.env.ConfigurableEnvironment org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration$InfoPropertiesConfiguration.environment; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.core.env.ConfigurableEnvironment] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private final org.springframework.core.env.ConfigurableEnvironment org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration$InfoPropertiesConfiguration.environment; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.core.env.ConfigurableEnvironment] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:561)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
    ... 16 common frames omitted
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.core.env.ConfigurableEnvironment] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1301)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1047)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:942)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:533)
    ... 18 common frames omitted

    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1210)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:118)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:686)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:320)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:957)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:946)
    at com.bettercloud.synchronizer.Application.main(Application.java:14)
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private final org.springframework.core.env.ConfigurableEnvironment org.springframework.boot.actuate.autoconfigure.EndpointAutoConfiguration$InfoPropertiesConfiguration.environment; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.core.env.ConfigurableEnvironment] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:561)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
    ... 16 more
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [org.springframework.core.env.ConfigurableEnvironment] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1301)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1047)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:942)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:533)
    ... 18 more
:bootRun FAILED