从单链表Java中删除第一个节点

Question

我有一个链表数据结构，我正在测试deleteInfo()函数。然而，当我试图删除链表中的最后一项时，我得到了一个错误。这个链表从顶部开始插入，所以在这个例子中，最后一个元素实际上是插入的第一个元素。

代码如下:

public lList deleteInfo(String outInfo) {
        if ( info == outInfo ) {
            lList link = nextList().deleteInfo( outInfo );
            info = link.info;
            nextList = link.nextList();
        }
        else if ( nextList() != null )
            nextList().deleteInfo( outInfo );
        return this;
    }
public void insert(String in_Info) {
        if ( isEmpty() == false ) {
            lList entry = new lList(); // New entry is created to store new list
            entry.info = info; //Store the current list's information into this list
            entry.nextList = nextList;
            nextList = entry; //Next list now points to the entry created
        }
        info = in_Info;
    }
public lList nextList() {
        if ( isEmpty() == false )
            return nextList;
        return null;
    }

谁能告诉我一个允许删除最后一个列表的方法?我知道问题是在第一个if语句，因为它可能试图访问一个空列表，因为最后一个列表没有nextList。但我不知道还有什么别的办法;所以任何帮助都很感谢

Answer 1

public lList deleteInfo(String outInfo) {
        if ( nextList() != null && nextList().info == outInfo ) {
            lList link = nextList();
            nextList = link.nextList();
        }
        else if (nextList() != null){
            nextList().deleteInfo( outInfo );
        }
        return this;
    }

Answer 2

你可能想要在第一个if中添加一个内部if来检查你是否删除了最后一个if:

 public lList deleteInfo(String outInfo) {
        if ( info == outInfo ) {
         if( nextList() == null ) {
               //delete current list as u want
               return this;
         }
            lList link = nextList().deleteInfo( outInfo );
            info = link.info;
            nextList = link.nextList();
        }
        else if ( nextList() != null )
            nextList().deleteInfo( outInfo );
        return this;
    }

Answer 3

这是我最终成功的方法:

//lList : deleteInfo()
//Pre: information to delete
//Post : List not containing information is returned
public lList deleteInfo(String outInfo) {
    if ( nextList() != null ) {
        lList link = nextList().deleteInfo( outInfo );
        if ( nextList().info == outInfo ) { //Handles information that is located at end of list
            nextList = link.nextList();
        }
        else if ( info == outInfo ){//Handles information that is located at beginning of list
            info = link.info;
            nextList = link.nextList();
        }
        else nextList().deleteInfo( outInfo );
    }
    return this;
}

请注意，当只有一个列表并且您试图删除该列表中的信息时，它不起作用。我认为这是件好事因为你不能取消对self