根據多個引數交換串列項

我有一個類似于下面的串列。我想根據我指定的規則對這個串列進行排序。如果有一個元素附加了串列元素，它必須在前排。

例如，由于 Id 為 2 的記錄的 RequiredCourse 欄位為 3，因此 Id 為 3 的元素必須位于 Id 為 2 的元素之前。為此，我創建了一個交換方法，如下所示。但是 Id 3 的記錄取決于 4，我無法正確創建排序。此外，它取決于 ID 為 8 及以下的 10。但是 9 沒有連接到任何東西。由于我更改了 ID 為 8 和 10 的記錄的位置，因此 8 位于 9 之后。

示例輸出應如下所示：

        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;
                }
            }
        }

使用上面的代碼有缺陷的輸出

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

預期產出

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

uj5u.com熱心網友回復：

問題是您想要“4 - ''”下方的專案“2 - 3”。我確信有一種方法可以改進我所做的事情，但這是 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}");
}

uj5u.com熱心網友回復：

我認為這很容易理解。

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);
        }
    }
}

您的通緝名單在output.

標籤：C＃ 列表 排序 交换

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