如何执行递归搜索? [英] How to perform a recursive search?

问题描述

我有一个Task类，可以包含相同类型的子任务

I have a Task class which can have sub tasks of the same type

public class Task
{
  public DateTime Start { get; set;}
  public DateTime Finish { get; set;}
  public List<Task> Tasks {get; set;}
  public DateTime FindTaskStartDate(Task task)
  {}
}

我应该如何执行递归搜索(也许可能是linq)以找到最早开始日期的任务?

How should i perform a recursive search (linq perhaps) to find the task with the earliest start date?

我最初的方法涉及太多的for循环，最终变得一团糟，并迅速失控.这是我的第二次尝试:

My initial approach involved too many for loops and it ended becoming a bit of a mess and quickly spiraling out of control. Here's my second attempt:

public DateTime FindTaskStartDate(Task task)
{
    DateTime startDate = task.Start;

    if(task.HasSubTasks())
    {
        foreach (var t in task.Tasks)
        {
            if (t.Start < startDate)
            {
                startDate = t.Start;

                if (t.HasSubTasks())
                {
                    //What next?
                    //FindTaskStartDate(t);
                }
            }
        }
    }

    return startDate;
}

有没有更好的解决方案来解决此问题?

Any nicer solutions out there to solve this problem?

谢谢

推荐答案

您是对的，在这里递归是正确的方法.这样的事情应该起作用:

You're right, recursion is the right approach here. Something like this should work:

public DateTime FindTaskStartDate(Task task)
{
    DateTime startDate = task.Start;

    foreach (var t in task.Tasks)
    {
        var subTaskDate = FindTaskStartDate(t);
        if (subTaskDate < startDate)
            startDate = subTaskDate;
    }

    return startDate;
}

我删除了task.HasSubTasks()的支票，因为这只会使代码更加复杂，而没有任何额外的好处.

I removed the check for task.HasSubTasks(), because it only makes the code more complicated without any added benefit.

如果您发现经常编写的代码需要遍历树中的所有任务，则可能需要使其更通用.例如，您可能有一个返回IEnumerable<Task>的方法，该方法返回树中的所有任务.这样，找到最小的开始日期就很容易了:

If you find your often write code that needs to walk all of the tasks in the tree, you might want to make this more general. For example, you could have a method that returns IEnumerable<Task> that returns all the tasks in the tree. Finding the smallest start date would then be as easy as:

IterateSubTasks(task).Min(t => t.Start)

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