将值与数组进行比较并获得最接近的值

我是C＃的新手，我正在努力学习这门语言。

你们能给我一个提示，我可以比较一个数组，从中选择最低值吗？

喜欢：

Double[] w = { 1000, 2000, 3000, 4000, 5000 }; double min = double.MaxValue; double max = double.MinValue; foreach (double value in w) { if (value  max) max = value; } Console.WriteLine(" min:", min); 

给我w的最低值，我现在怎么比较？

如果我有：

 int p = 1001 + 2000; // 3001 

我如何比较数组列表，并发现（3000）值是我的“搜索值”最接近的值？

Answer 1

你可以用一些简单的数学来做到这一点，并且有不同的方法。

LINQ

 Double searchValue = ...; Double nearest = w.Select(p => new { Value = p, Difference = Math.Abs(p - searchValue) }) .OrderBy(p => p.Difference) .First().Value; 

手动

 Double[] w = { 1000, 2000, 3000, 4000, 5000 }; Double searchValue = 3001; Double currentNearest = w[0]; Double currentDifference = Math.Abs(currentNearest - searchValue); for (int i = 1; i < w.Length; i++) { Double diff = Math.Abs(w[i] - searchValue); if (diff < currentDifference) { currentDifference = diff; currentNearest = w[i]; } } 

Answer 2

 Double[] w = { 1000, 2000, 3000, 4000, 5000 }; var minimumValueFromArray = w.Min(); 

产生

1000 ，正如预期的那样，导致我们执行Enumerable.Min 。

Enumerable.Max也是如此 ，以确定最大值：

 Double[] w = { 1000, 2000, 3000, 4000, 5000 }; var maximumValueFromArray = w.Max(); 

考虑到你要与double.MinValue和double.MaxValue进行比较，我认为你只想从数组中选择最小和最大的值。

如果这不是您要搜索的内容，请澄清。

Answer 3

根据您的代码，您可以通过非常简单的方式实现此目的

  Double[] w = { 1000, 2000, 3000, 4000, 5000 }; // it has to be sorted double search = 3001; double lowerClosest = 0; double upperClosest = 0; for (int i = 1; i < w.Length; i++) { if (w[i] > search) { upperClosest = w[i]; break; // interrupts your foreach } } for (int i = w.Length-1; i >=0; i--) { if (w[i] <= search) { lowerClosest = w[i]; break; // interrupts your foreach } } Console.WriteLine(" lowerClosest:{0}", lowerClosest); Console.WriteLine(" upperClosest:{0}", upperClosest); if (upperClosest - search > search - lowerClosest) Console.WriteLine(" Closest:{0}", lowerClosest); else Console.WriteLine(" Closest:{0}", upperClosest); Console.ReadLine(); 

根据搜索值的位置，这将小于O（n）

Answer 4

  Performance wise custom code will be more use full. List results; int targetNumber = 0; int nearestValue=0; if (results.Any(ab => ab == targetNumber )) { nearestValue= results.FirstOrDefault(i => i == targetNumber ); } else { int greaterThanTarget = 0; int lessThanTarget = 0; if (results.Any(ab => ab > targetNumber )) { greaterThanTarget = results.Where(i => i > targetNumber ).Min(); } if (results.Any(ab => ab < targetNumber )) { lessThanTarget = results.Where(i => i < targetNumber ).Max(); } if (lessThanTarget == 0 ) { nearestValue= greaterThanTarget; } else if (greaterThanTarget == 0) { nearestValue= lessThanTarget; } else if (targetNumber - lessThanTarget < greaterThanTarget - targetNumber ) { nearestValue= lessThanTarget; } else { nearestValue= greaterThanTarget; } }