删除int数组列表中的重复项
有一个int数组列表,如:
List intArrList = new List(); intArrList.Add(new int[3] { 0, 0, 0 }); intArrList.Add(new int[5] { 20, 30, 10, 4, 6 }); //this intArrList.Add(new int[3] { 1, 2, 5 }); intArrList.Add(new int[5] { 20, 30, 10, 4, 6 }); //this intArrList.Add(new int[3] { 12, 22, 54 }); intArrList.Add(new int[5] { 1, 2, 6, 7, 8 }); intArrList.Add(new int[4] { 0, 0, 0, 0 });
你将如何删除重复(重复我的意思是列表的元素具有相同的长度和相同的数字)。
在示例中,我将删除元素{ 20, 30, 10, 4, 6 }
因为它被发现两次
我正在考虑按元素大小对列表进行排序,然后将每个元素循环反对rest,但我不知道该怎么做。
其他问题是,如果使用像哈希这样的其他结构会更好……如果是这样如何使用它?
使用GroupBy
:
var result = intArrList.GroupBy(c => String.Join(",", c)) .Select(c => c.First().ToList()).ToList();
结果:
{0,0,0}
{20,30,10,4,6}
{1,2,5}
{12,22,54}
{1,2,6,7,8}
{0,0,0,0}
编辑 :如果你想{1,2,3,4}
等于{2,3,4,1}
你需要像这样使用OrderBy
:
var result = intArrList.GroupBy(p => string.Join(", ", p.OrderBy(c => c))) .Select(c => c.First().ToList()).ToList();
编辑2 :为了帮助理解LINQ GroupBy
解决方案的工作原理,请考虑以下方法:
public List FindDistinctWithoutLinq(List lst) { var dic = new Dictionary(); foreach (var item in lst) { string key = string.Join(",", item.OrderBy(c=>c)); if (!dic.ContainsKey(key)) { dic.Add(key, item); } } return dic.Values.ToList(); }
您可以定义自己的IEqualityComparer
实现,并将其与IEnumerable.Distinct
一起使用:
class MyComparer : IEqualityComparer { public int GetHashCode(int[] instance) { return 0; } // TODO: better HashCode for arrays public bool Equals(int[] instance, int[] other) { if (other == null || instance == null || instance.Length != other.Length) return false; return instance.SequenceEqual(other); } }
现在编写此代码以仅获取列表的不同值:
var result = intArrList.Distinct(new MyComparer());
但是,如果您想要不同的排列,也应该以这种方式实现比较器:
public bool Equals(int[] instance, int[] other) { if (ReferenceEquals(instance, other)) return true; // this will return true when both arrays are NULL if (other == null || instance == null) return false; return instance.All(x => other.Contains(x)) && other.All(x => instance.Contains(x)); }
编辑:为了更好的GetashCode
实现,你可以看看这篇文章 ,也在@ Mick的回答中提出。
从这里和这里提升代码。 一个更通用的GetHashCode实现会使这更通用,但我相信下面的实现是最强大的
class Program { static void Main(string[] args) { List intArrList = new List(); intArrList.Add(new int[3] { 0, 0, 0 }); intArrList.Add(new int[5] { 20, 30, 10, 4, 6 }); //this intArrList.Add(new int[3] { 1, 2, 5 }); intArrList.Add(new int[5] { 20, 30, 10, 4, 6 }); //this intArrList.Add(new int[3] { 12, 22, 54 }); intArrList.Add(new int[5] { 1, 2, 6, 7, 8 }); intArrList.Add(new int[4] { 0, 0, 0, 0 }); var test = intArrList.Distinct(new IntArrayEqualityComparer()); Console.WriteLine(test.Count()); Console.WriteLine(intArrList.Count()); } public class IntArrayEqualityComparer : IEqualityComparer { public bool Equals(int[] x, int[] y) { return ArraysEqual(x, y); } public int GetHashCode(int[] obj) { int hc = obj.Length; for (int i = 0; i < obj.Length; ++i) { hc = unchecked(hc * 17 + obj[i]); } return hc; } static bool ArraysEqual(T[] a1, T[] a2) { if (ReferenceEquals(a1, a2)) return true; if (a1 == null || a2 == null) return false; if (a1.Length != a2.Length) return false; EqualityComparer comparer = EqualityComparer .Default; for (int i = 0; i < a1.Length; i++) { if (!comparer.Equals(a1[i], a2[i])) return false; } return true; } } }
编辑: IEqualityComparer的通用实现,适用于任何类型的数组: -
public class ArrayEqualityComparer : IEqualityComparer { public bool Equals(T[] x, T[] y) { if (ReferenceEquals(x, y)) return true; if (x == null || y == null) return false; if (x.Length != y.Length) return false; EqualityComparer comparer = EqualityComparer .Default; for (int i = 0; i < x.Length; i++) { if (!comparer.Equals(x[i], y[i])) return false; } return true; } public int GetHashCode(T[] obj) { int hc = obj.Length; for (int i = 0; i < obj.Length; ++i) { hc = unchecked(hc * 17 + obj[i].GetHashCode()); } return hc; } }
Edit2 :如果数组内的整数排序无关紧要,我会的
var test = intArrList.Select(a => a.OrderBy(e => e).ToArray()).Distinct(comparer).ToList();
List CopyString1 = new List(); CopyString1.AddRange(intArrList); List CopyString2 = new List(); CopyString2.AddRange(intArrList); for (int i = 0; i < CopyString2.Count(); i++) { for (int j = i; j < CopyString1.Count(); j++) { if (i != j && CopyString2[i].Count() == CopyString1[j].Count()) { var cnt = 0; for (int k = 0; k < CopyString2[i].Count(); k++) { if (CopyString2[i][k] == CopyString1[j][k]) cnt++; else break; } if (cnt == CopyString2[i].Count()) intArrList.RemoveAt(i); } } }
使用BenchmarkDotNet比较@ S.Akbari和@ Mick的解决方案
编辑:
SAkbari_FindDistinctWithoutLinq对ContainsKey进行了冗余调用,所以我添加了更快的版本:SAkbari_FindDistinctWithoutLinq2
方法| 意思是| 错误| StdDev | --------------------------------- | ---------:| ----- -----:| ----------:| SAkbari_FindDistinctWithoutLinq | 4.021我们| 0.0723我们| 0.0676 us | SAkbari_FindDistinctWithoutLinq2 | 3.930我们| 0.0529我们| 0.0495我们| SAkbari_FindDistinctLinq | 5.597我们| 0.0264我们| 0.0234我们| Mick_UsingGetHashCode | 6.339我们| 0.0265我们| 0.0248我们|
BenchmarkDotNet = v0.10.13,OS = Windows 10 Redstone 3 [1709,Fall Creators Update](10.0.16299.248) 英特尔酷睿i7-7700 CPU 3.60GHz(Kaby Lake),1个CPU,8个逻辑内核和4个物理内核 频率= 3515625 Hz,分辨率= 284.4444 ns,定时器= TSC .NET Core SDK = 2.1.100 [主持人]:.NET Core 2.0.5(CoreCLR 4.6.26020.03,CoreFX 4.6.26018.01),64位RyuJIT DefaultJob:.NET Core 2.0.5(CoreCLR 4.6.26020.03,CoreFX 4.6.26018.01),64位RyuJIT
基准测试:
using BenchmarkDotNet.Attributes; using BenchmarkDotNet.Running; using System; using System.Collections.Generic; using System.Linq; namespace ConsoleApp1 { public class Program { List intArrList = new List { new int[] { 0, 0, 0 }, new int[] { 20, 30, 10, 4, 6 }, //this new int[] { 1, 2, 5 }, new int[] { 20, 30, 10, 4, 6 }, //this new int[] { 12, 22, 54 }, new int[] { 1, 2, 6, 7, 8 }, new int[] { 0, 0, 0, 0 } }; [Benchmark] public List SAkbari_FindDistinctWithoutLinq() => FindDistinctWithoutLinq(intArrList); [Benchmark] public List SAkbari_FindDistinctWithoutLinq2() => FindDistinctWithoutLinq2(intArrList); [Benchmark] public List SAkbari_FindDistinctLinq() => FindDistinctLinq(intArrList); [Benchmark] public List Mick_UsingGetHashCode() => FindDistinctLinq(intArrList); static void Main(string[] args) { var summary = BenchmarkRunner.Run(); } public static List FindDistinctWithoutLinq(List lst) { var dic = new Dictionary(); foreach (var item in lst) { string key = string.Join(",", item.OrderBy(c => c)); if (!dic.ContainsKey(key)) { dic.Add(key, item); } } return dic.Values.ToList(); } public static List FindDistinctWithoutLinq2(List lst) { var dic = new Dictionary(); foreach (var item in lst) dic.TryAdd(string.Join(",", item.OrderBy(c => c)), item); return dic.Values.ToList(); } public static List FindDistinctLinq(List lst) { return lst.GroupBy(p => string.Join(", ", p.OrderBy(c => c))) .Select(c => c.First().ToArray()).ToList(); } public static List UsingGetHashCode(List lst) { return lst.Select(a => a.OrderBy(e => e).ToArray()).Distinct(new IntArrayEqualityComparer()).ToList(); } } public class IntArrayEqualityComparer : IEqualityComparer { public bool Equals(int[] x, int[] y) { return ArraysEqual(x, y); } public int GetHashCode(int[] obj) { int hc = obj.Length; for (int i = 0; i < obj.Length; ++i) { hc = unchecked(hc * 17 + obj[i]); } return hc; } static bool ArraysEqual(T[] a1, T[] a2) { if (ReferenceEquals(a1, a2)) return true; if (a1 == null || a2 == null) return false; if (a1.Length != a2.Length) return false; EqualityComparer comparer = EqualityComparer .Default; for (int i = 0; i < a1.Length; i++) { if (!comparer.Equals(a1[i], a2[i])) return false; } return true; } } }
输入清单;
List> initList = new List>(); initList.Add(new List { 0, 0, 0 }); initList.Add(new List { 20, 30, 10, 4, 6 }); //this initList.Add(new List { 1, 2, 5 }); initList.Add(new List { 20, 30, 10, 4, 6 }); //this initList.Add(new List { 12, 22, 54 }); initList.Add(new List { 1, 2, 6, 7, 8 }); initList.Add(new List { 0, 0, 0, 0 });
您可以创建结果列表,在添加元素之前,您可以检查它是否已添加。 我只是比较列表计数并使用p.Except(item).Any()
调用来检查列表是否包含该元素。
List> returnList = new List>(); foreach (var item in initList) { if (returnList.Where(p => !p.Except(item).Any() && !item.Except(p).Any() && p.Count() == item.Count() ).Count() == 0) returnList.Add(item); }
您可以使用HashSet。 HashSet是用于保证唯一性的集合,您可以比较集合,Intersect,Union上的项目。 等等
优点:没有重复,易于操作数据组,更有效缺点:您无法获取集合中的特定项目,例如:list [0]不适用于HashSet。 您只能枚举项目。 例如foreach
这是一个例子:
using System; using System.Collections.Generic; namespace ConsoleApp2 { class Program { static void Main(string[] args) { HashSet> intArrList = new HashSet>(new HashSetIntComparer()); intArrList.Add(new HashSet (3) { 0, 0, 0 }); intArrList.Add(new HashSet (5) { 20, 30, 10, 4, 6 }); //this intArrList.Add(new HashSet (3) { 1, 2, 5 }); intArrList.Add(new HashSet (5) { 20, 30, 10, 4, 6 }); //this intArrList.Add(new HashSet (3) { 12, 22, 54 }); intArrList.Add(new HashSet (5) { 1, 2, 6, 7, 8 }); intArrList.Add(new HashSet (4) { 0, 0, 0, 0 }); // Checking the output foreach (var item in intArrList) { foreach (var subHasSet in item) { Console.Write("{0} ", subHasSet); } Console.WriteLine(); } Console.Read(); } private class HashSetIntComparer : IEqualityComparer> { public bool Equals(HashSet x, HashSet y) { // SetEquals does't set anything. It's a method for compare the contents of the HashSet. // Such a poor name from .Net return x.SetEquals(y); } public int GetHashCode(HashSet obj) { //TODO: implemente a better HashCode return base.GetHashCode(); } } } } Output: 0 20 30 10 4 6 1 2 5 12 22 54 1 2 6 7 8
注意:由于0重复多次,因此HashSet仅将0视为0。 如果需要在0 0 0 0和0 0 0之间进行差异化,则可以将
HashSet
替换> for HashSet
> HashSet
并将Comparer实现为List。> for HashSet
>
您可以使用此链接了解如何比较列表: https : //social.msdn.microsoft.com/Forums/en-US/2ff3016c-bd61-4fec-8f8c-7b6c070123fa/c-compare-two-lists-of -objects?论坛= csharplanguage
如果您想了解有关馆藏和数据类型的更多信息,本课程是学习它的理想场所: https : //app.pluralsight.com/player? course = ccsharp-collections&author = verson -robinson&name = ccsharp -collections-fundamentals-m9- 套夹&= 1&模式=活
使用MoreLINQ,使用DistinctBy可以非常简单。
var result = intArrList.DistinctBy(x => string.Join(",", x));
类似于GroupBy的答案,如果你想区分不管订单只是在连接中的顺序。
var result = intArrList.DistinctBy(x => string.Join(",", x.OrderBy(y => y)));
编辑 :这是它的实现方式
public static IEnumerable DistinctBy(this IEnumerable source, Func keySelector, IEqualityComparer comparer) { if (source == null) throw new ArgumentNullException(nameof(source)); if (keySelector == null) throw new ArgumentNullException(nameof(keySelector)); return _(); IEnumerable _() { var knownKeys = new HashSet(comparer); foreach (var element in source) { if (knownKeys.Add(keySelector(element))) yield return element; } } }
所以,如果你不需要MoreLINQ,你可以使用这样的方法:
private static IEnumerable GetUniqueArrays(IEnumerable source) { var knownKeys = new HashSet(); foreach (var element in source) { if (knownKeys.Add(string.Join(",", element))) yield return element; } }