Question

我有List<double[]>我希望用数组创建新列表，女巫完全相同。我这样试试：

var query = li.GroupBy(x => x)
               .Where(g => g.Count() > 1)
               .Select(y => y.Key)
               .ToList();

但是在所有列表查询都有0个元素之后......我做错了什么？

好的，所以：

list[0] = double[4] {1.4,0.5,3.6,1.2},
list[1] = double[4] {0.3,0.4,3.1,1.2}
list[2] = double[4] {1.4,0.5,3.6,1.2}

在我的新名单中，我只想：

new_list[0] = double[4] {1.4,0.5,3.6,1.2}

Answer 1

List<double[]> lists = new List<double[]>{
    new[]{1.4,0.5,3.6,1.2},
    new[]{0.3,0.4,3.1,1.2},
    new[]{1.4,0.5,3.6,1.2}
};

var query = lists.SelectMany(x => x) // <-- You need this
                .GroupBy(x => x)
                .Where(g => g.Count() > 1)
                .Select(y => y.Key)
                .ToList();

Answer 2

当它们是复杂对象（如数组）时，您应该使用自定义相等比较器来查找重复项。

    class DoubleArrayComparer : IEqualityComparer<double[]>
    {
        private DoubleArrayComparer() { }

        public static readonly DoubleArrayComparer Instance = new DoubleArrayComparer();

        public bool Equals(double[] x, double[] y)
        {
            return Enumerable.SequenceEqual(x, y);
        }

        public int GetHashCode(double[] obj)
        {
            //TODO: should implement better
            return 0;
        }
    }

    static void Main(string[] args)
    {
        List<double[]> li = new List<double[]>{
            new[]{1.4,0.5,3.6,1.2},
            new[]{0.3,0.4,3.1,1.2},
            new[]{1.4,0.5,3.6,1.2}
        };

        var query = li.GroupBy(x => x, DoubleArrayComparer.Instance)
            .Where(g => g.Count() == 1)
            .Select(y => y.Key)
            .ToList();
    }

Answer 3

如果我正确理解您的问题，您只需要在输入查询中重复的数组。因为没有简单的方法可以按整个数组内容进行分组，所以您可以尝试将数组转换为字符串并按该字符串分组：

var results = list.GroupBy(a => String.Join(",", a.Select(d => d.ToString())))
                  .Where(g => g.Count() > 1)
                  .Select(g => g.First())
                  .ToList();

Answer 4

这个解决方案怎么样？

public class ArrayComparer : IEqualityComparer<double[]>
    {

        public bool Equals(double[] x, double[] y)
        {
            return x.SequenceEqual(y);
        }

        public int GetHashCode(double[] obj)
        {
            return base.GetHashCode();
        }
    }

var list = new double[] {1.4, 0.5, 3.6, 1.2};
var list2 = new double[] { 0.3, 0.4, 3.1, 1.2 };
var list3 = new double[] { 1.4, 0.5, 3.6, 1.2 };

var lst = new List<double[]> {list, list2, list3};

var newList = lst.Where(x => lst.Except(new List<double[]> {x}).Contains(x,new ArrayComparer()))
                         .Distinct(new ArrayComparer())
                         .ToList();

调试中的另一个例子：

enter image description here

Answer 5

使用Intersect

var query = lists.Select(x => x) 
            .Where(y => x.Intersect(y).Count == x.Count)
            .Select(y => y)
            .ToList();

这个psaude代码 - 当我靠近我的Windows机器时，我可以查看

双数组列表 - 如何检测重复数据

5 个答案: