根据多个参数交换列表项

Question

我有一个如下所示的列表。我想根据我指定的规则对这个列表进行排序。如果有一个列表元素附加到的元素，它必须在前排。

例如，由于 ID 为 2 的记录的 RequiredCourse 字段为 3，因此 ID 为 3 的元素必须位于 ID 为 2 的元素之前。为此，我创建了一个 swap 方法，如下所示。但是 ID 为 3 的记录依赖于 4，我无法正确创建排序。此外，它取决于 ID 为 8 及以下的 10。但是 9 没有连接到任何东西。由于我更改了 id 为 8 和 10 的记录的位置，所以 8 在 9 之后。

示例输出应如下所示：

        var list = new List<Course>();

        list.Add(new Course { Id = 1 });
        list.Add(new Course { Id = 2, RequiredCourse = "3" });
        list.Add(new Course { Id = 3, RequiredCourse = "4" });
        list.Add(new Course { Id = 4 });
        list.Add(new Course { Id = 5 });
        list.Add(new Course { Id = 6 });
        list.Add(new Course { Id = 7 });
        list.Add(new Course { Id = 8, RequiredCourse = "10" });
        list.Add(new Course { Id = 9 });
        list.Add(new Course { Id = 10 });
        list = list.OrderBy(i => i.Id).ThenBy(i => i.RequiredCourse).ToList();

        var copy = new List<Course>(list);

        for (int i = 0; i < copy.Count; i++)
        {
            if (!string.IsNullOrEmpty(copy[i].RequiredCourse) && Int32.Parse(copy[i].RequiredCourse) > copy[i].Id)
            {
                var index = list.FindIndex(k => k.Id == Int32.Parse(copy[i].RequiredCourse));
                if (index > -1)
                {
                    var temp = list[i];
                    list[i] = list[index];
                    list[index] = temp;
                }
            }
        }

使用上述代码的输出有缺陷

1                
3                4
4                
2                3
5                
6                
7                
10               
9                
8                10

预期输出

1                
4                
3                4
2                3
5                
6                
7                
10               
8                10
9

Answer 1

问题是您想要“4 - ''”下方的项目“2 - 3”。我确信有一种方法可以改进我所做的，但这里是 1.0 版：

var list = new List<Course>();
    
list.Add(new Course { Id = 1 });
list.Add(new Course { Id = 2, RequiredCourse = "3" });
list.Add(new Course { Id = 3, RequiredCourse = "4" });
list.Add(new Course { Id = 4 });
list.Add(new Course { Id = 5 });
list.Add(new Course { Id = 6 });
list.Add(new Course { Id = 7 });
list.Add(new Course { Id = 8, RequiredCourse = "10" });
list.Add(new Course { Id = 9 });
list.Add(new Course { Id = 10 });

// isolating items with RequiredCourse
var withRequired = (
    from o in list
    where !string.IsNullOrWhiteSpace(o.RequiredCourse)
    select o
).ToList();
list = list.Except(withRequired).ToList();

// First I arrange the items without "RequiredCourse" with their respective ones.
for (var i = 0; i < list.Count; i++)
{
    var primary = list[i];
    var parents =
        withRequired
            .Where(o => o.RequiredCourse == primary.Id.ToString())
            .OrderBy(o => o.Id)
            .ToList();
    var children = (
        from o in withRequired.Except(parents)
        join o2 in parents
            on o.Id.ToString() equals o2.RequiredCourse
            into grp
        from o3 in grp
        orderby o3.Id descending
        select o3
    ).ToList();

    if (!parents.Any())
    {
        continue;
    }

    i++;
    foreach (var p in parents)
    {
        list.Insert(i++, p);
        foreach (var c in children.Where(o => p.Id.ToString() == o.RequiredCourse))
        {
            list.Insert(i++, c);
        }
    }
}

// retrieving items that only link to items that have RequiredCourse
var childOfChildren = withRequired.Except(list).ToList();

// Then I arrange items with RequiredCourses that are linked to other items with RequiredCourses.
for (var i = 0; i < list.Count; i++)
{
    var primary = list[i];
    var children = (
        from o in childOfChildren
        where primary.Id.ToString() == o.RequiredCourse
        orderby o.Id descending
        select o
    ).ToList();

    if (!children.Any())
    {
        continue;
    }

    i++;
    list.InsertRange(i, children);
}

// CONSOLE APPLICATION PART
foreach (var o in list)
{
    if (string.IsNullOrEmpty(o.RequiredCourse))
    {
        o.RequiredCourse = "-";
    }

    Console.WriteLine($"Course: {o.Id} - {o.RequiredCourse}");
}

Answer 2

我觉得这很容易理解。

var list = new List<Course>();

list.Add(new Course { Id = 1 });
list.Add(new Course { Id = 2, RequiredCourse = "3" });
list.Add(new Course { Id = 3, RequiredCourse = "4" });
list.Add(new Course { Id = 4 });
list.Add(new Course { Id = 5 });
list.Add(new Course { Id = 6 });
list.Add(new Course { Id = 7 });
list.Add(new Course { Id = 8, RequiredCourse = "10" });
list.Add(new Course { Id = 9 });
list.Add(new Course { Id = 10 });

var output = new List<Course>();
var toProcess = new SortedDictionary<int, Course>(list.ToDictionary(c => c.Id));
var pendingAdd = new Stack<Course>();

while (toProcess.Count > 0)
{
    Course currentCourse = toProcess.First().Value;
    if (string.IsNullOrEmpty(currentCourse.RequiredCourse))
    {
        // Course has no dependency, process it.
        output.Add(currentCourse);
        toProcess.Remove(currentCourse.Id);
    }
    else
    {
        int courseId = currentCourse.Id;
        // Course has dependency. Trace down linked courses.
        while (toProcess.ContainsKey(courseId) && !string.IsNullOrEmpty(toProcess[courseId].RequiredCourse))
        {
            pendingAdd.Push(toProcess[courseId]);
            courseId = int.Parse(toProcess[courseId].RequiredCourse);
        }
        // dont forget to add the "top-level" course for the dependency chain
        pendingAdd.Push(toProcess[courseId]);

        // Add in reverse depdency order using Stack
        while (pendingAdd.Count > 0)
        {
            var course = pendingAdd.Pop();
            output.Add(course);
            toProcess.Remove(course.Id);
        }
    }
}

您的通缉名单在output。

Answer 3

可以通过回归来完成，示例代码未针对其他情况进行测试。仅针对给定数据进行测试。

public static void Main()
{
    var list = new List<Course>();

    list.Add(new Course { Id = 1 });
    list.Add(new Course { Id = 2, RequiredCourse = "3" });
    list.Add(new Course { Id = 3, RequiredCourse = "4" });
    list.Add(new Course { Id = 4 });
    list.Add(new Course { Id = 5 });
    list.Add(new Course { Id = 6 });
    list.Add(new Course { Id = 7 });
    list.Add(new Course { Id = 8, RequiredCourse = "10" });
    list.Add(new Course { Id = 9 });
    list.Add(new Course { Id = 10 });
    list = list.OrderBy(i => i.Id).ThenBy(i => i.RequiredCourse).ToList();

    var copy = new List<Course>();
        
    foreach(var tt in list)
    {
        //Console.WriteLine(tt.Id + " " + tt.RequiredCourse);
        populateParent(list,ref copy, tt);
        
        if(!copy.Any(p => p.Id == tt.Id))
            copy.Add(tt);
    }
    
    foreach(var tt in copy)
    {
        Console.WriteLine(tt.Id + " " + tt.RequiredCourse);
    }
}

public static Course populateParent(List<Course> inputList,ref List<Course> outputList, Course current)
{
    if(string.IsNullOrWhiteSpace(current.RequiredCourse))
    {
        if(!outputList.Any(p => p.Id == current.Id))
            outputList.Add(current);
        return current;
    }
    else
    {
        var tt = inputList.First(p => current.RequiredCourse != null && p.Id == int.Parse(current.RequiredCourse) );
        
        var parent = populateParent(inputList,ref outputList,tt);
        if(!outputList.Any(p => p.Id == parent.Id))
            outputList.Add(parent);
        
        if(!outputList.Any(p => p.Id == tt.Id))
            outputList.Add(tt);
        return tt;
    }   
}

code in dotnetfiddle

根据多个参数交换列表项

Swap list item according to multiple parameters

c#

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list