C# 在列表中合并两个或多个T<;T>;基于条件
我有以下课程:C# 在列表中合并两个或多个T<;T>;基于条件,c#,linq,collections,C#,Linq,Collections,我有以下课程: public class FactoryOrder { public string Text { get; set; } public int OrderNo { get; set; } } 和保存FactoryOrder列表的集合 List<FactoryOrder>() 我的要求是合并FactoryOrder的文本,其中orderNo按顺序排列,并保留合并FactoryOrder的较低orderN
public class FactoryOrder
{
public string Text { get; set; }
public int OrderNo { get; set; }
}
和保存FactoryOrder列表的集合
List<FactoryOrder>()
我的要求是合并FactoryOrder的文本,其中orderNo按顺序排列,并保留合并FactoryOrder的较低orderNo
-因此,结果输出将是
FactoryOrder("Apple Orange",20) //Merged Apple and Orange and retained Lower OrderNo 20
FactoryOrder("WaterMelon",42)
FactoryOrder("JackFruit",51)
FactoryOrder("Grapes mango Cherry",71)//Merged Grapes,Mango,cherry and retained Lower OrderNo 71
我是Linq的新手,所以不知道该怎么做。任何帮助或指示都将不胜感激我不确定使用一个可理解的LINQ表达式是否可以做到这一点。使用简单的枚举即可:
private static IEnumerable<FactoryOrder> Merge(IEnumerable<FactoryOrder> orders)
{
var enumerator = orders.OrderBy(x => x.OrderNo).GetEnumerator();
FactoryOrder previousOrder = null;
FactoryOrder mergedOrder = null;
while (enumerator.MoveNext())
{
var current = enumerator.Current;
if (mergedOrder == null)
{
mergedOrder = new FactoryOrder(current.Text, current.OrderNo);
}
else
{
if (current.OrderNo == previousOrder.OrderNo + 1)
{
mergedOrder.Text += current.Text;
}
else
{
yield return mergedOrder;
mergedOrder = new FactoryOrder(current.Text, current.OrderNo);
}
}
previousOrder = current;
}
if (mergedOrder != null)
yield return mergedOrder;
}
私有静态IEnumerable合并(IEnumerable订单)
{
var枚举器=orders.OrderBy(x=>x.OrderNo).GetEnumerator();
FactoryOrder previousOrder=null;
FactoryOrder mergedOrder=null;
while(枚举数.MoveNext())
{
var current=枚举数。当前值;
if(mergedOrder==null)
{
mergedOrder=新工厂订单(current.Text,current.OrderNo);
}
其他的
{
if(current.OrderNo==previousOrder.OrderNo+1)
{
mergedOrder.Text+=当前的.Text;
}
其他的
{
收益合并器;
mergedOrder=新工厂订单(current.Text,current.OrderNo);
}
}
前序=当前;
}
if(mergedOrder!=null)
收益合并器;
}
这假设
FactoryOrder
有一个接受文本和订单号的构造函数。如注释所示,如果您的逻辑严重依赖于连续项,那么LINQ不是最简单的方法。使用一个简单的循环
您可以先使用LINQ:orders.OrderBy(x=>x.OrderNo)
您的样品:
刚刚编写了一个方法,它结构紧凑,性能相当好:
static List<FactoryOrder> MergeValues(List<FactoryOrder> dirtyList)
{
FactoryOrder[] temp1 = dirtyList.ToArray();
int index = -1;
for (int i = 1; i < temp1.Length; i++)
{
if (temp1[i].OrderNo - temp1[i - 1].OrderNo != 1) { index = -1; continue; }
if(index == -1 ) index = dirtyList.IndexOf(temp1[i - 1]);
dirtyList[index].Text += " " + temp1[i].Text;
dirtyList.Remove(temp1[i]);
}
return dirtyList;
}
静态列表合并值(列表目录列表)
{
FactoryOrder[]temp1=dirtyList.ToArray();
int指数=-1;
for(int i=1;i
使用副作用的Linq实施:
var groupId = 0;
var previous = Int32.MinValue;
var grouped = GetItems()
.OrderBy(x => x.OrderNo)
.Select(x =>
{
var @group = x.OrderNo != previous + 1 ? (groupId = x.OrderNo) : groupId;
previous = x.OrderNo;
return new
{
GroupId = group,
Item = x
};
})
.GroupBy(x => x.GroupId)
.Select(x => new FactoryOrder(
String.Join(" ", x.Select(y => y.Item.Text).ToArray()),
x.Key))
.ToArray();
foreach (var item in grouped)
{
Console.WriteLine(item.Text + "\t" + item.OrderNo);
}
输出:
Apple Orange 20
WaterMelon 42
JackFruit 51
Grapes mango Cherry 71
或者,使用生成器扩展方法消除副作用
public static class IEnumerableExtensions
{
public static IEnumerable<IList<T>> MakeSets<T>(this IEnumerable<T> items, Func<T, T, bool> areInSameGroup)
{
var result = new List<T>();
foreach (var item in items)
{
if (!result.Any() || areInSameGroup(result[result.Count - 1], item))
{
result.Add(item);
continue;
}
yield return result;
result = new List<T> { item };
}
if (result.Any())
{
yield return result;
}
}
}
输出相同,但代码更易于遵循和维护。LINQ+顺序处理= 虽然没有说使用
Aggregate
始终是最好的选择。for(each)
循环中的顺序处理通常有助于更好地读取代码(参见Tim的答案)。无论如何,这里有一个纯LINQ解决方案
它循环遍历订单,并首先将它们收集到字典中,其中连续订单的第一个Id
为Key
,订单的集合为Value
。然后它使用字符串生成一个结果。Join
:
类别:
class FactoryOrder
{
public FactoryOrder(int id, string name)
{
this.Id = id;
this.Name = name;
}
public int Id { get; set; }
public string Name { get; set; }
}
该方案:
IEnumerable<FactoryOrder> orders =
new[]
{
new FactoryOrder(20, "Apple"),
new FactoryOrder(21, "Orange"),
new FactoryOrder(22, "Pear"),
new FactoryOrder(42, "WaterMelon"),
new FactoryOrder(51, "JackFruit"),
new FactoryOrder(71, "Grapes"),
new FactoryOrder(72, "Mango"),
new FactoryOrder(73, "Cherry"),
};
var result = orders.OrderBy(t => t.Id).Aggregate(new Dictionary<int, List<FactoryOrder>>(),
(dir, curr) =>
{
var prevId = dir.SelectMany(d => d.Value.Select(v => v.Id))
.OrderBy(i => i).DefaultIfEmpty(-1)
.LastOrDefault();
var newKey = dir.Select(d => d.Key).OrderBy(i => i).LastOrDefault();
if (prevId == -1 || curr.Id - prevId > 1)
{
newKey = curr.Id;
}
if (!dir.ContainsKey(newKey))
{
dir[newKey] = new List<FactoryOrder>();
}
dir[newKey].Add(curr);
return dir;
}, c => c)
.Select(t => new
{
t.Key,
Items = string.Join(" ", t.Value.Select(v => v.Name))
}).ToList();
IEnumerable订单=
新[]
{
新工厂订单(20,“苹果”),
新工厂订单(21,“橙色”),
新工厂订单(22,“Pear”),
新工厂订单(42,“西瓜”),
新工厂订单(51,“菠萝蜜”),
新工厂订单(71,“葡萄”),
新工厂订单(72,“芒果”),
新工厂订单(73,“樱桃”),
};
var result=orders.OrderBy(t=>t.Id).Aggregate(新字典(),
(直接,当前)=>
{
var prevId=dir.SelectMany(d=>d.Value.Select(v=>v.Id))
.OrderBy(i=>i).DefaultIfEmpty(-1)
.LastOrDefault();
var newKey=dir.Select(d=>d.Key).OrderBy(i=>i.LastOrDefault();
如果(prevId==-1 | | curr.Id-prevId>1)
{
newKey=curr.Id;
}
如果(!dir.ContainsKey(newKey))
{
dir[newKey]=新列表();
}
目录[newKey]。添加(当前);
返回目录;
},c=>c)
.选择(t=>new
{
t、 钥匙,
Items=string.Join(“,t.Value.Select(v=>v.Name))
}).ToList();
正如您所看到的,这里发生的事情并不简单,而且当有“许多”项时,它的性能可能会很差,因为不断增长的字典会被一次又一次地访问
这是一个冗长的说法:不要使用聚合。如果您的逻辑严重依赖于连续项,那么LINQ不是最简单的方法。使用一个简单的循环。你可以先用LINQ订购:
orders.Orderby(x=>x.OrderNo)
@TimSchmelter我甚至不认为有一种“理智的”“纯粹的”LINQ方法可以做到这一点…@xanatos:这取决于你所说的纯粹。有LINQ扩展方法,因此可以通过相邻项对其进行分组。但是他们只是隐藏了很多复杂的代码。类似。@xanatos:但即使是该实现也不关心属性的连续值,而是关心序列中属性中具有相同值的连续项。所以你是对的,我不知道任何实现。@TimSchmelter显然构建一个完整的程序并将其隐藏在LINQ后面不是“纯粹的”:-,但它仍然是一个很好的解决方案。
public static class IEnumerableExtensions
{
public static IEnumerable<IList<T>> MakeSets<T>(this IEnumerable<T> items, Func<T, T, bool> areInSameGroup)
{
var result = new List<T>();
foreach (var item in items)
{
if (!result.Any() || areInSameGroup(result[result.Count - 1], item))
{
result.Add(item);
continue;
}
yield return result;
result = new List<T> { item };
}
if (result.Any())
{
yield return result;
}
}
}
var grouped = GetItems()
.OrderBy(x => x.OrderNo)
.MakeSets((prev, next) => next.OrderNo == prev.OrderNo + 1)
.Select(x => new FactoryOrder(
String.Join(" ", x.Select(y => y.Text).ToArray()),
x.First().OrderNo))
.ToList();
foreach (var item in grouped)
{
Console.WriteLine(item.Text + "\t" + item.OrderNo);
}
class FactoryOrder
{
public FactoryOrder(int id, string name)
{
this.Id = id;
this.Name = name;
}
public int Id { get; set; }
public string Name { get; set; }
}
IEnumerable<FactoryOrder> orders =
new[]
{
new FactoryOrder(20, "Apple"),
new FactoryOrder(21, "Orange"),
new FactoryOrder(22, "Pear"),
new FactoryOrder(42, "WaterMelon"),
new FactoryOrder(51, "JackFruit"),
new FactoryOrder(71, "Grapes"),
new FactoryOrder(72, "Mango"),
new FactoryOrder(73, "Cherry"),
};
var result = orders.OrderBy(t => t.Id).Aggregate(new Dictionary<int, List<FactoryOrder>>(),
(dir, curr) =>
{
var prevId = dir.SelectMany(d => d.Value.Select(v => v.Id))
.OrderBy(i => i).DefaultIfEmpty(-1)
.LastOrDefault();
var newKey = dir.Select(d => d.Key).OrderBy(i => i).LastOrDefault();
if (prevId == -1 || curr.Id - prevId > 1)
{
newKey = curr.Id;
}
if (!dir.ContainsKey(newKey))
{
dir[newKey] = new List<FactoryOrder>();
}
dir[newKey].Add(curr);
return dir;
}, c => c)
.Select(t => new
{
t.Key,
Items = string.Join(" ", t.Value.Select(v => v.Name))
}).ToList();