C# 您可以使用 LINQ 或 LAMBDA 表达式在一行中对字符串进行反向排序吗
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原文地址: http://stackoverflow.com/questions/1152887/
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Can you reverse order a string in one line with LINQ or a LAMBDA expression
提问by Student for Life
Not that I would want to use this practically (for many reasons) but out of strict curiousity I would like to know if there is a way to reverse order a string using LINQ and/or LAMBDA expressions in one line of code, without utilising any framework "Reverse" methods.
并不是说我想实际使用它（出于多种原因），而是出于严格的好奇心，我想知道是否有一种方法可以在一行代码中使用 LINQ 和/或 LAMBDA 表达式对字符串进行反向排序，而不使用任何框架“反向”方法。
e.g.
例如
string value = "reverse me";
string reversedValue = (....);
and reversedValue will result in "em esrever"
和 reversedValue 将导致“em esrever”
EDITClearly an impractical problem/solution I know this, so don't worry it's strictly a curiosity question around the LINQ/LAMBDA construct.
编辑显然是一个不切实际的问题/解决方案我知道这一点，所以不要担心它严格来说是一个围绕 LINQ/LAMBDA 构造的好奇问题。
采纳答案by Mehrdad Afshari
I don't see a practical use for this but just for the sake of fun:
我认为这没有实际用途，只是为了好玩：
new string(Enumerable.Range(1, input.Length).Select(i => input[input.Length - i]).ToArray())
回答by Jon Skeet
Well, I can do it in one very long line, even without using LINQ or a lambda:
好吧，即使不使用 LINQ 或 lambda，我也可以在很长的一行中完成：
string original = "reverse me"; char[] chars = original.ToCharArray(); char[] reversed = new char[chars.Length]; for (int i=0; i < chars.Length; i++) reversed[chars.Length-i-1] = chars[i]; string reversedValue = new string(reversed);
(Dear potential editors: do notunwrap this onto multiple lines. The whole point is that it's a single line, as per the sentence above it and the question.)
（亲爱的潜在编辑：不要把它拆成多行。重点是它是一行，根据上面的句子和问题。）
However, if I saw anyone avoiding using framework methods for the sake of it, I'd question their sanity.
但是，如果我看到有人为此避免使用框架方法，我会质疑他们的理智。
Note that this doesn't use LINQ at all. A LINQ answer would be:
请注意，这根本不使用 LINQ。LINQ 的答案是：
string reverseValue = new string(original.Reverse().ToArray());
Avoiding using Reverse, but using OrderByDescending instead:
避免使用 Reverse，而是使用 OrderByDescending：
string reverseValue = new string(original.Select((c, index) => new { c, index })
.OrderByDescending(x => x.index)
.Select(x => x.c)
.ToArray());
Blech. I like Mehrdad's answer though. Of course, all of these are far less efficient than the straightforward approach.
布莱克。不过，我喜欢 Mehrdad 的回答。当然，所有这些都远不如直截了当的方法有效。
Oh, and they're all wrong, too. Reversing a string is more complex than reversing the order of the code points. Consider combining characters, surrogate pairs etc...
哦，他们也都错了。反转字符串比反转代码点的顺序更复杂。考虑组合字符、代理对等...
回答by Dejan Stani?
Variant with recursive lambda:
递归 lambda 的变体：
var value = "reverse me";
Func<String, String> f = null; f = s => s.Length == 1 ? s : f(s.Substring(1)) + s[0];
var reverseValue = f(value);
LP, Dejan
LP, 德扬
回答by Joe Chung
var reversedValue = value.ToCharArray()
.Select(ch => ch.ToString())
.Aggregate<string>((xs, x) => x + xs);
回答by Ben Lings
You can use Aggregateto prepend each Charto the reversed string:
您可以使用Aggregate将每个前置Char到反向字符串：
"reverse me".Aggregate("", (acc, c) => c + acc);
回答by shlomiw
new string(value.Reverse().ToArray())
回答by rsa
var reversedValue= "reverse me".Reverse().ToArray();
回答by The Void
In addition to one previous post here is a more performant solution.
除了之前的一篇文章外，这里还有一个更高效的解决方案。
var actual0 = "reverse me".Aggregate(new StringBuilder(), (x, y) => x.Insert(0, y)).ToString();
回答by Vishav Premlall
public static string Reverse(string word)
{
int index = word.Length - 1;
string reversal = "";
//for each char in word
for (int i = index; index >= 0; index--)
{
reversal = reversal + (word.Substring(index, 1));
Console.WriteLine(reversal);
}
return reversal;
}
Quite simple. So, from this point on, I have a single method that reverses a string, that doesn't use any built-in Reverse functions.
非常简单。所以，从现在开始，我有一个反转字符串的方法，它不使用任何内置的 Reverse 函数。
So in your main method, just go,
所以在你的主要方法中，去吧，
Console.WriteLine(Reverse("Some word"));
Console.WriteLine(Reverse("Some word"));
Technically that's your one liner :P
从技术上讲，这是你的一个班轮：P
回答by Jeppe Stig Nielsen
If we need to support combining characters and surrogate pairs:
如果我们需要支持组合字符和代理对：
// This method tries to handle:
// (1) Combining characters
// These are two or more Unicode characters that are combined into one glyph.
// For example, try reversing "Not nai\u0308ve.". The diaresis (¨) should stay over the i, not move to the v.
// (2) Surrogate pairs
// These are Unicode characters whose code points exceed U+FFFF (so are not in "plane 0").
// To be represented with 16-bit 'char' values (which are really UTF-16 code units), one character needs *two* char values, a so-called surrogate pair.
// For example, try "The sphere \U0001D54A and the torus \U0001D54B.". The and the should be preserved, not corrupted.
var value = "reverse me"; // or "Not nai\u0308ve.", or "The sphere \U0001D54A and the torus \U0001D54B.".
var list = new List<string>(value.Length);
var enumerator = StringInfo.GetTextElementEnumerator(value);
while (enumerator.MoveNext())
{
list.Add(enumerator.GetTextElement());
}
list.Reverse();
var result = string.Concat(list);
Documentation: MSDN: System.Globalization.StringInfoClass
