在双向链接列表中搜索c＃

Question

I'm writing an application which is using a doubly linked list. I need to implement search in this list. There is a list of employees with the name, id, department. What I need to do is to find the specified employee by her/his last name. Any ideas, how it's possible to implement?

Answer 1

Please do not reinvent the wheel. All classes for this are already in .Net - just initialize LinkedList and use Enumerable.FirstOrDefault to search:

  LinkedList<Employee> employees = ....
  var firstWithIdSeven =  employees.FirstOrDefault(e => e.Id == 7); // assuming id is int

Note that if you need frequent search by some subset of parameters using Dictionary with custom comparer would be more efficient.

Answer 2

If this is for actual C# code, you should be using the collections that come with the system (such as LinkedList ).

For educational purposes, the algorithm is as follows:

def find(lastName):
    set curr to head
    while curr <> null:
        if curr.lastName == lastName:
            return curr
        curr = curr.next
    return null

Translating that into C# (or any other procedural language) should be relatively easy.

Answer 3

Trolling level 7 : recursive lambda

If you are looking for exotic implemetations - check out High Level Function Confusion with Lambda/LINQ expressions in C# that discusses iteration with recursive lambda expression.

So let's say your node is

 class Employee
 {
     // code to initialize omitted
     public Employee Next { get;}
     public int Id { get;}
 }

Now we can use following recursive lambda (converting to anonymous recursive lambda is exercise for readers)

Func<
    Func<Employee, bool>,     // condition to continue iteration
    Func<Employee, Employee>, // "next" function
    Func<Employee, Employee>  // resulting iterator method
    > Loop = null;
Loop = (c , f ) => n => c(n) ? Loop(c , f ) ( f (n)): n;
Func<Employee, Employee> findIdSevenStartingFrom = Loop(
       n => !(n == null || n.Id == 7), // condition to continue search
       n => n.Next );                  // iterator function 

Now with findIdSevenStartingFrom we can pass any element of the list and search to the end to find it by Id.

var listHead = new Employee{ Id = 6, Next = new Employee { Id = 7 } };
var item = findIdSevenStartingFrom(listHead);

Answer 4

I think you are looking for something like this:

Employee:

public class Employee
{
    public string FirstName {get; set;}
    public string LastName {get; set;}
}

Double linked node:

public class DoubleLinkedList
{
    public Employee Employee {get; set;}
    public DoubleLinkedList Next {get; set;}
    public DoubleLinkedList Prev {get; set;}
}

Function to find employee by name in the list:

public Employee FindByName(DoubleLinkedList startNode, string name)
{
    var currentNode = startNode;
    while(currentNode != null)
    {
        if(currentNode.Employee.LastName == name) 
        {
            return currentNode.Employee; // Found
        }
        currentNode = currentNode.Next;
    }
    return null; // Not found
}