[英]Iterate through list of items to their parent and parent to parent level
我有一個要求遍歷具有 n 級層次結構的項目列表,並且我想獲取所選項目 ID 的自下而上元素。
例如,下面是原始數據
ID ParentID ItemName Category
1 -1 Chai Breweries
4 -1 Mouse-pad Electronic
3 1 GST Taxes
2 1 Spices
5 4 Mobile
6 3 My Tax
我想在 C# 中編程以進行迭代並顯示例如,如果我為方法 6 傳遞 ID 參數,那么它應該打印 output 如下
ParentID=3, Name=My Tax, Category=Taxes
如果我將 ID 參數作為 2 傳遞,那么 output 應該是相似的
ParentID=1, Name=Spices, Category=Breweries
請幫助我實現此功能可能是使用通用集合或任何算法都會有幫助
我嘗試過使用 List 並加上 LINQ 的 select 很多,但是使用此選項,我只能獲取當前項目,但如果當前項目沒有與之關聯的類別,則不能獲取父類別值。 還嘗試添加遞歸方法,但不確定如何構建結束 output,使用遞歸我們應該只獲取當前項目。
好的,根據以下評論,我使用了遞歸 function 如下
class Program
{
static void Main(string[] args)
{
int categoryId = 202;
var products = GetProducts();
var product = products.FirstOrDefault(p => p.ID == categoryId);
var output = GetProductRecursively(products, categoryId, string.Empty);
Console.WriteLine(output);
Console.Read();
}
public static string GetProductRecursively(List<Product> products, int parentId, string output)
{
var product = products.FirstOrDefault(p => p.ParentID == parentId);
StringBuilder stringBuilder = new StringBuilder();
if (string.IsNullOrEmpty(product.Category))
{
if (string.IsNullOrEmpty(output))
{
stringBuilder.Append($"ParentCategoryID={ product.ParentID}, Name={ product.ItemName}, Keywords=");
GetProductRecursively(products, product.ParentID, stringBuilder.ToString());
}
else
GetProductRecursively(products, product.ParentID, output);
}
else
stringBuilder.Append($"{output}{product.Category}");
return stringBuilder.ToString();
}
public static List<Product> GetProducts()
{
var products = new List<Product>();
products.Add(new Product { ID = 1, ParentID = -1, ItemName = "Chai", Category = "Breweries" });
products.Add(new Product { ID = 4, ParentID = -1, ItemName = "Mouse-pad", Category= "Electronic" });
products.Add(new Product { ID = 3, ParentID = 1, ItemName = "GST", Category= "Taxes" });
products.Add(new Product { ID = 2, ParentID = 1, ItemName = "Spices" });
products.Add(new Product { ID = 5, ParentID = 4, ItemName = "Mobile" });
products.Add(new Product { ID = 6, ParentID = 3, ItemName = "My Tax" });
return products;
}
}
public class Product
{
public int ID { get; set; }
public int ParentID { get; set; }
public string ItemName { get; set; }
public string Category { get; set; }
}
但是,在一次迭代中,它返回父 ID 的類別,但由於它處於遞歸狀態,因此它繼續完成早期迭代的工作,因此此時類別始終返回“”(empty.string)
非遞歸解決方案可能如下所示:
var productId = 6;
var products = GetProducts();
var productDict = products // create dictionary to search for products by id
.GroupBy(p => p.ID)
.ToDictionary(p => p.Key, g => g.First());
var product = productDict[productId];
// create loop state variables
string category = null;
var currProduct = product;
// cycle while category not found
while (category == null)
{
// or there is no parent product
if (!productDict.ContainsKey(currProduct.ParentID))
{
break;
}
currProduct = productDict[currProduct.ParentID];
category = currProduct.Category;
}
Console.WriteLine($"{category}-{product.ItemName}");
沒有任何代碼,我只能為您的問題提供“默認”答案。
要解決您的問題,您必須在類中實現 function 以獲取實例的父級。
要獲得絕對父級(對象本身沒有父級),您必須實現一個 function,只要它有父級,它就會調用自己。
好的,終於讓它以正確的邏輯工作,工作代碼如下
class Program
{
static void Main(string[] args)
{
int productId = 6;
var products = GetProducts();
var product = products.FirstOrDefault(p => p.ID == productId);
var output = GetProductRecursively(products, productId, string.Empty);
Console.WriteLine(output);
Console.Read();
}
public static string GetProductRecursively(List<Product> products, int Id, string output)
{
var product = products.FirstOrDefault(p => p.ID == Id);
StringBuilder stringBuilder = new StringBuilder();
if (string.IsNullOrEmpty(output))
output = stringBuilder.Append($"ParentCategoryID={ product.ParentID}, Name={ product.ItemName}, Keywords=").ToString();
if (string.IsNullOrEmpty(product.Category))
{
return GetProductRecursively(products, product.ParentID, output);
}
else
output += $"{product.Category}";
return output;
}
public static List<Product> GetProducts()
{
var products = new List<Product>();
products.Add(new Product { ID = 1, ParentID = -1, ItemName = "Chai", Category = "Breweries" });
products.Add(new Product { ID = 4, ParentID = -1, ItemName = "Mouse-pad", Category = "Electronic" });
products.Add(new Product { ID = 3, ParentID = 1, ItemName = "GST", Category = "Taxes" });
products.Add(new Product { ID = 2, ParentID = 1, ItemName = "Spices" });
products.Add(new Product { ID = 5, ParentID = 4, ItemName = "Mobile" });
products.Add(new Product { ID = 6, ParentID = 3, ItemName = "My Tax" });
return products;
}
}
public class Product
{
public int ID { get; set; }
public int ParentID { get; set; }
public string ItemName { get; set; }
public string Category { get; set; }
}
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