Question

给定一个整数数组（+ ve和-ve数是无序的），什么是LINQ语句来查找总和最接近0的两个数字

E.g int[] a = new int[]{2, 56, -11, 15, 12, 10, 43, -59, -13}

在上面的整数集{-11，10}和{12中，-13}是两个最接近{{1}的整数}}

除了LINQ的以下基本查询之外，我无法得到太多，因为我不知道如何继续，

Answer 1

如果它可以是集合中的任何两个值，那么你可以这样做......

var set = new int[] { 2, 56, -11, 15, 12, 10, 43, -59, -13 };

var ret = (from a in set
           from b in set
           orderby Math.Abs(a + b)
           select new
           {
               a,
               b
           }).First();

Console.WriteLine(ret); // {a: -11, b:12 }

如果你想要对大型集合稍微提高性能（并且可以假设混合了负值和正值），你可以这样做。

var set = new int[] { 2, 56, -11, 15, 12, 10, 43, -59, -13 };

var ret = (from a in set.Where(x => x >= 0)
           from b in set.Where(y => y < 0)
           orderby Math.Abs(a + b)
           select new
           {
               a,
               b
           }).First();

Console.WriteLine(ret); // { a= 12, b= -11}

因为你现在想要整个匹配集，不包括与自己的匹配......

var set = new int[] { 2, 56, -11, 15, 12, 10, 43, -59, -13 };

var ret = from a in set
          from b in set
          where a != b
          let c = new { a, b }
          group c by Math.Abs(c.a + c.b);

var minset = ret.First(i => i.Key == ret.Min(j => j.Key))
                .Select(s=>s);

Console.WriteLine(minset.Aggregate(new StringBuilder(), 
                                   (sb,v)=>sb.Append(v)
                                             .AppendLine()
                                  ));

/*
    { a = -11, b = 12 }
    { a = -11, b = 10 }
    { a = 12, b = -11 }
    { a = 12, b = -13 }
    { a = 10, b = -11 }
    { a = -13, b = 12 }
*/

重复数据删除......

var set = new[] { 2, 56, -11, 15, 12, 10, 43, -59, -13 };

var ret = from a in set
            from b in set
            where a != b
            let c = new { a, b }
            group c by Math.Abs(c.a + c.b);

var minset = ret.First(i => i.Key == ret.Min(j => j.Key))
                .Select(s => new { a = Math.Min(s.a, s.b), b = Math.Max(s.a, s.b) })
                .Distinct();

Console.WriteLine(minset.Aggregate(new StringBuilder(), 
                                    (sb, v) => sb.Append(v)
                                                .AppendLine()));

/*
    { a = -11, b = 12 }
    { a = -11, b = 10 }
    { a = -13, b = 12 }
*/

Answer 2

var data = new [] { 2, 56, -11, 15, 12, 10, 43, -59, -13 };

// TODO : assert data.Length >= 2
var query = from i in Enumerable.Range (0, data.Length - 2)
            from j in Enumerable.Range (i + 1, data.Length - 1 - i)
            let x = data[i] let y = data[j]
            group new { x, y } by Math.Abs (x + y) into g
            orderby g.Key select g;

Console.WriteLine (string.Join ("\n", query.First ()));

{x = -11，y = 12}
  {x = -11，y = 10}
  {x = 12，y = -13}

LINQ获取数组中的两个整数，其总和最接近于零

2 个答案: