如何用一个空格replace多个空格
比方说，我有一个string，如：
"Hello how are you doing?" 我想要一个把多个空格变成一个空格的函数。
所以我会得到：
"Hello how are you doing?"
我知道我可以使用正则expression式或调用
string s = "Hello how are you doing?".replace(" "," ");
但是我不得不多次调用它以确保所有顺序的空格都被replace为一个。
有没有内置的方法呢？
string cleanedString = System.Text.RegularExpressions.Regex.Replace(dirtyString,@"\s+"," ");
这个问题并不像其他海报所说的那样简单（而且正如我原先所认为的那样） – 因为这个问题不是很确切。
“空格”和“空白”之间有区别。 如果你只是指空格，那么你应该使用" {2,}"的正则expression式。 如果你的意思是任何空白，这是另一回事。 所有的空格都应该转换为空格吗？ 开始和结束时会发生什么？
对于下面的基准，我假设你只关心空间，而且你不想对单个空间做任何事情，即使在开始和结束时也是如此。
请注意，正确性总是比性能更重要。 Split / Join解决scheme删除任何前导/尾随空白（即使只是单个空格）的事实是不正确的，只要您指定的要求（当然可能不完整）。
基准使用MiniBench 。
using System; using System.Text.RegularExpressions; using MiniBench; internal class Program { public static void Main(string[] args) { int size = int.Parse(args[0]); int gapBetweenExtraSpaces = int.Parse(args[1]); char[] chars = new char[size]; for (int i=0; i < size/2; i += 2) { // Make sure there actually *is* something to do chars[i*2] = (i % gapBetweenExtraSpaces == 1) ? ' ' : 'x'; chars[i*2 + 1] = ' '; } // Just to make sure we don't have a \0 at the end // for odd sizes chars[chars.Length-1] = 'y'; string bigString = new string(chars); // Assume that one form works :) string normalized = NormalizeWithSplitAndJoin(bigString); var suite = new TestSuite<string, string>("Normalize") .Plus(NormalizeWithSplitAndJoin) .Plus(NormalizeWithRegex) .RunTests(bigString, normalized); suite.Display(ResultColumns.All, suite.FindBest()); } private static readonly Regex MultipleSpaces = new Regex(@" {2,}", RegexOptions.Compiled); static string NormalizeWithRegex(string input) { return MultipleSpaces.Replace(input, " "); } // Guessing as the post doesn't specify what to use private static readonly char[] Whitespace = new char[] { ' ' }; static string NormalizeWithSplitAndJoin(string input) { string[] split = input.Split (Whitespace, StringSplitOptions.RemoveEmptyEntries); return string.Join(" ", split); } }
一些testing运行：
c:\Users\Jon\Test>test 1000 50 ============ Normalize ============ NormalizeWithSplitAndJoin 1159091 0:30.258 22.93 NormalizeWithRegex 26378882 0:30.025 1.00 c:\Users\Jon\Test>test 1000 5 ============ Normalize ============ NormalizeWithSplitAndJoin 947540 0:30.013 1.07 NormalizeWithRegex 1003862 0:29.610 1.00 c:\Users\Jon\Test>test 1000 1001 ============ Normalize ============ NormalizeWithSplitAndJoin 1156299 0:29.898 21.99 NormalizeWithRegex 23243802 0:27.335 1.00
在这里，第一个数字是迭代次数，第二个是需要的时间，第三个是缩放分数，1.0是最好的。
这表明，至less在某些情况下（包括这个），正则expression式可以超越Split / Join解决scheme，有时甚至会有非常显着的差距。
但是，如果您更改为“全部空白”要求，则“拆分/连接” 似乎会胜出。 正如往常一样，魔鬼是在细节…
虽然现有的答案是好的，但我想指出一个不起作用的方法：
public static string DontUseThisToCollapseSpaces(string text) { while (text.IndexOf(" ") != -1) { text = text.Replace(" ", " "); } return text; }
这可以永远循环。 有人在乎为什么？ （几年前，当我被问及新闻组的问题时，我才发现这个问题……有人真的遇到了这个问题。）
定期expressoin将是最简单的方法。 如果以正确的方式编写正则expression式，则不需要多次调用。
将其更改为：
string s = System.Text.RegularExpressions.Regex.Replace(s, @"\s{2,}", " ");
正如已经指出的那样，这很容易通过正则expression式来完成。 我只是补充说，你可能想添加一个.trim（）来摆脱前/后空白。
我分享我使用的东西，因为看起来我已经想出了一些不同的东西。 我已经使用了一段时间，这对我来说足够快。 我不确定它是如何叠加起来的。 我在分隔的文件编写器中使用它，并通过它每次运行一个字段的大型数据表。
public static string NormalizeWhiteSpace(string S) { string s = S.Trim(); bool iswhite = false; int iwhite; int sLength = s.Length; StringBuilder sb = new StringBuilder(sLength); foreach(char c in s.ToCharArray()) { if(Char.IsWhiteSpace(c)) { if (iswhite) { //Continuing whitespace ignore it. continue; } else { //New WhiteSpace //Replace whitespace with a single space. sb.Append(" "); //Set iswhite to True and any following whitespace will be ignored iswhite = true; } } else { sb.Append(c.ToString()); //reset iswhitespace to false iswhite = false; } } return sb.ToString(); }
使用Jon Skeet发布的testing程序，我试着看看能否得到一个手写的循环来加快运行速度。
每次我都可以击败NormalizeWithSplitAndJoin，但是只能input1000,5的NormalizeWithRegex。
static string NormalizeWithLoop(string input) { StringBuilder output = new StringBuilder(input.Length); char lastChar = '*'; // anything other then space for (int i = 0; i < input.Length; i++) { char thisChar = input[i]; if (!(lastChar == ' ' && thisChar == ' ')) output.Append(thisChar); lastChar = thisChar; } return output.ToString(); }
我没有看到抖动产生的机器代码，但是我期望的问题是调用StringBuilder.Append（）所花费的时间，要做得更好，需要使用不安全的代码。
所以Regex.Replace（）是非常快，很难打！
这是我工作的解决scheme。 没有RegEx和String.Split。
public static string TrimWhiteSpace(this string Value) { StringBuilder sbOut = new StringBuilder(); if (!string.IsNullOrEmpty(Value)) { bool IsWhiteSpace = false; for (int i = 0; i < Value.Length; i++) { if (char.IsWhiteSpace(Value[i])) //Comparion with WhiteSpace { if (!IsWhiteSpace) //Comparison with previous Char { sbOut.Append(Value[i]); IsWhiteSpace = true; } } else { IsWhiteSpace = false; sbOut.Append(Value[i]); } } } return sbOut.ToString(); }
所以你可以：
string cleanedString = dirtyString.TrimWhiteSpace();
Regex regex = new Regex(@"\W+"); string outputString = regex.Replace(inputString, " ");
VB.NET Linha.Split（“”）.ToList（）。Where（Function（x）x <>“”）.ToArray
C＃Linha.Split（“”）.ToList（）。其中（x => x <>“”）.ToArray（）
享受Linq = D的力量
一个快速的额外的空白卸妆…这是最快的一个，是基于菲利普马查多的就地副本。
static string InPlaceCharArray(string str) { var len = str.Length; var src = str.ToCharArray(); int dstIdx = 0; bool lastWasWS = false; for (int i = 0; i < len; i++) { var ch = src[i]; if (src[i] == '\u0020') { if (lastWasWS == false) { src[dstIdx++] = ch; lastWasWS = true; } } else { lastWasWS = false; src[dstIdx++] = ch; } } return new string(src, 0, dstIdx); }
基准…
InPlaceCharArraySpaceOnly由Felipe Machado在CodeProject 2015上进行修改，并由Sunsetquest进行修改，以便进行多空间移除。 时间：3.75蜱
InPlaceCharArray by Felipe Machado 2015，稍微修改了Sunsetquest的多空间删除。 时间6.50蜱 （也支持标签）
由Jon Skeet提供的 SplitAndJoinOnSpace。 时间：13.25蜱
StringBuilder by fubo 时间：13.5 滴答 （也支持标签）
正则expression式由Jon Skeet编译。 时间：17蜱
由String S的 StringBuilder 2013年时间：30.5蜱
正则expression式与布兰登非编译时间：63.25蜱
StringBuilder由user214147 时间：77.125蜱
用非编译Tim Hoolihan的正则expression式时间：147.25蜱
基准代码…
using System; using System.Text.RegularExpressions; using System.Diagnostics; using System.Threading; using System.Text; static class Program { public static void Main(string[] args) { long seed = ConfigProgramForBenchmarking(); Stopwatch sw = new Stopwatch(); string warmup = "This is a Warm up function for best benchmark results." + seed; string input1 = "Hello World, how are you doing?" + seed; string input2 = "It\twas\t \tso nice to\t\t see you \tin 1950. \t" + seed; string correctOutput1 = "Hello World, how are you doing?" + seed; string correctOutput2 = "It\twas\tso nice to\tsee you in 1950. " + seed; string output1,output2; //warm-up timer function sw.Restart(); sw.Stop(); sw.Restart(); sw.Stop(); long baseVal = sw.ElapsedTicks; // InPlace Replace by Felipe Machado but modified by Ryan for multi-space removal (http://www.codeproject.com/Articles/1014073/Fastest-method-to-remove-all-whitespace-from-Strin) output1 = InPlaceCharArraySpaceOnly (warmup); sw.Restart(); output1 = InPlaceCharArraySpaceOnly (input1); output2 = InPlaceCharArraySpaceOnly (input2); sw.Stop(); Console.WriteLine("InPlaceCharArraySpaceOnly : " + (sw.ElapsedTicks - baseVal)); Console.WriteLine(" Trial1:(spaces only) " + (output1 == correctOutput1 ? "PASS " : "FAIL ")); Console.WriteLine(" Trial2:(spaces+tabs) " + (output2 == correctOutput2 ? "PASS " : "FAIL ")); // InPlace Replace by Felipe R. Machado and slightly modified by Ryan for multi-space removal (http://www.codeproject.com/Articles/1014073/Fastest-method-to-remove-all-whitespace-from-Strin) output1 = InPlaceCharArray(warmup); sw.Restart(); output1 = InPlaceCharArray(input1); output2 = InPlaceCharArray(input2); sw.Stop(); Console.WriteLine("InPlaceCharArray: " + (sw.ElapsedTicks - baseVal)); Console.WriteLine(" Trial1:(spaces only) " + (output1 == correctOutput1 ? "PASS " : "FAIL ")); Console.WriteLine(" Trial2:(spaces+tabs) " + (output2 == correctOutput2 ? "PASS " : "FAIL ")); //Regex with non-compile Tim Hoolihan (https://stackoverflow.com/a/1279874/2352507) string cleanedString = output1 = Regex.Replace(warmup, @"\s+", " "); sw.Restart(); output1 = Regex.Replace(input1, @"\s+", " "); output2 = Regex.Replace(input2, @"\s+", " "); sw.Stop(); Console.WriteLine("Regex by Tim Hoolihan: " + (sw.ElapsedTicks - baseVal)); Console.WriteLine(" Trial1:(spaces only) " + (output1 == correctOutput1 ? "PASS " : "FAIL ")); Console.WriteLine(" Trial2:(spaces+tabs) " + (output2 == correctOutput2 ? "PASS " : "FAIL ")); //Regex with compile by Jon Skeet (https://stackoverflow.com/a/1280227/2352507) output1 = MultipleSpaces.Replace(warmup, " "); sw.Restart(); output1 = MultipleSpaces.Replace(input1, " "); output2 = MultipleSpaces.Replace(input2, " "); sw.Stop(); Console.WriteLine("Regex with compile by Jon Skeet: " + (sw.ElapsedTicks - baseVal)); Console.WriteLine(" Trial1:(spaces only) " + (output1 == correctOutput1 ? "PASS " : "FAIL ")); Console.WriteLine(" Trial2:(spaces+tabs) " + (output2 == correctOutput2 ? "PASS " : "FAIL ")); //Split And Join by Jon Skeet (https://stackoverflow.com/a/1280227/2352507) output1 = SplitAndJoinOnSpace(warmup); sw.Restart(); output1 = SplitAndJoinOnSpace(input1); output2 = SplitAndJoinOnSpace(input2); sw.Stop(); Console.WriteLine("Split And Join by Jon Skeet: " + (sw.ElapsedTicks - baseVal)); Console.WriteLine(" Trial1:(spaces only) " + (output1 == correctOutput1 ? "PASS " : "FAIL ")); Console.WriteLine(" Trial2:(spaces+tabs) " + (output2 == correctOutput2 ? "PASS " : "FAIL ")); //Regex by Brandon (https://stackoverflow.com/a/1279878/2352507 output1 = Regex.Replace(warmup, @"\s{2,}", " "); sw.Restart(); output1 = Regex.Replace(input1, @"\s{2,}", " "); output2 = Regex.Replace(input2, @"\s{2,}", " "); sw.Stop(); Console.WriteLine("Regex by Brandon: " + (sw.ElapsedTicks - baseVal)); Console.WriteLine(" Trial1:(spaces only) " + (output1 == correctOutput1 ? "PASS " : "FAIL ")); Console.WriteLine(" Trial2:(spaces+tabs) " + (output2 == correctOutput2 ? "PASS " : "FAIL ")); //StringBuilder by user214147 (https://stackoverflow.com/a/2156660/2352507 output1 = user214147(warmup); sw.Restart(); output1 = user214147(input1); output2 = user214147(input2); sw.Stop(); Console.WriteLine("StringBuilder by user214147: " + (sw.ElapsedTicks - baseVal)); Console.WriteLine(" Trial1:(spaces only) " + (output1 == correctOutput1 ? "PASS " : "FAIL ")); Console.WriteLine(" Trial2:(spaces+tabs) " + (output2 == correctOutput2 ? "PASS " : "FAIL ")); //StringBuilder by fubo (https://stackoverflow.com/a/27502353/2352507 output1 = fubo(warmup); sw.Restart(); output1 = fubo(input1); output2 = fubo(input2); sw.Stop(); Console.WriteLine("StringBuilder by fubo: " + (sw.ElapsedTicks - baseVal)); Console.WriteLine(" Trial1:(spaces only) " + (output1 == correctOutput1 ? "PASS " : "FAIL ")); Console.WriteLine(" Trial2:(spaces+tabs) " + (output2 == correctOutput2 ? "PASS " : "FAIL ")); //StringBuilder by David S 2013 (https://stackoverflow.com/a/16035044/2352507) output1 = SingleSpacedTrim(warmup); sw.Restart(); output1 = SingleSpacedTrim(input1); output2 = SingleSpacedTrim(input2); sw.Stop(); Console.WriteLine("StringBuilder(SingleSpacedTrim) by David S: " + (sw.ElapsedTicks - baseVal)); Console.WriteLine(" Trial1:(spaces only) " + (output1 == correctOutput1 ? "PASS " : "FAIL ")); Console.WriteLine(" Trial2:(spaces+tabs) " + (output2 == correctOutput2 ? "PASS " : "FAIL ")); } // InPlace Replace by Felipe Machado and slightly modified by Ryan for multi-space removal (http://www.codeproject.com/Articles/1014073/Fastest-method-to-remove-all-whitespace-from-Strin) static string InPlaceCharArray(string str) { var len = str.Length; var src = str.ToCharArray(); int dstIdx = 0; bool lastWasWS = false; for (int i = 0; i < len; i++) { var ch = src[i]; if (src[i] == '\u0020') { if (lastWasWS == false) { src[dstIdx++] = ch; lastWasWS = true; } } else { lastWasWS = false; src[dstIdx++] = ch; } } return new string(src, 0, dstIdx); } // InPlace Replace by Felipe R. Machado but modified by Ryan for multi-space removal (http://www.codeproject.com/Articles/1014073/Fastest-method-to-remove-all-whitespace-from-Strin) static string InPlaceCharArraySpaceOnly (string str) { var len = str.Length; var src = str.ToCharArray(); int dstIdx = 0; bool lastWasWS = false; //Added line for (int i = 0; i < len; i++) { var ch = src[i]; switch (ch) { case '\u0020': //SPACE case '\u00A0': //NO-BREAK SPACE case '\u1680': //OGHAM SPACE MARK case '\u2000': // EN QUAD case '\u2001': //EM QUAD case '\u2002': //EN SPACE case '\u2003': //EM SPACE case '\u2004': //THREE-PER-EM SPACE case '\u2005': //FOUR-PER-EM SPACE case '\u2006': //SIX-PER-EM SPACE case '\u2007': //FIGURE SPACE case '\u2008': //PUNCTUATION SPACE case '\u2009': //THIN SPACE case '\u200A': //HAIR SPACE case '\u202F': //NARROW NO-BREAK SPACE case '\u205F': //MEDIUM MATHEMATICAL SPACE case '\u3000': //IDEOGRAPHIC SPACE case '\u2028': //LINE SEPARATOR case '\u2029': //PARAGRAPH SEPARATOR case '\u0009': //[ASCII Tab] case '\u000A': //[ASCII Line Feed] case '\u000B': //[ASCII Vertical Tab] case '\u000C': //[ASCII Form Feed] case '\u000D': //[ASCII Carriage Return] case '\u0085': //NEXT LINE if (lastWasWS == false) //Added line { src[dstIdx++] = ch; //Added line lastWasWS = true; //Added line } continue; default: lastWasWS = false; //Added line src[dstIdx++] = ch; break; } } return new string(src, 0, dstIdx); } static readonly Regex MultipleSpaces = new Regex(@" {2,}", RegexOptions.Compiled); //Split And Join by Jon Skeet (https://stackoverflow.com/a/1280227/2352507) static string SplitAndJoinOnSpace(string input) { string[] split = input.Split(new char[] { ' '}, StringSplitOptions.RemoveEmptyEntries); return string.Join(" ", split); } //StringBuilder by user214147 (https://stackoverflow.com/a/2156660/2352507 public static string user214147(string S) { string s = S.Trim(); bool iswhite = false; int iwhite; int sLength = s.Length; StringBuilder sb = new StringBuilder(sLength); foreach (char c in s.ToCharArray()) { if (Char.IsWhiteSpace(c)) { if (iswhite) { //Continuing whitespace ignore it. continue; } else { //New WhiteSpace //Replace whitespace with a single space. sb.Append(" "); //Set iswhite to True and any following whitespace will be ignored iswhite = true; } } else { sb.Append(c.ToString()); //reset iswhitespace to false iswhite = false; } } return sb.ToString(); } //StringBuilder by fubo (https://stackoverflow.com/a/27502353/2352507 public static string fubo(this string Value) { StringBuilder sbOut = new StringBuilder(); if (!string.IsNullOrEmpty(Value)) { bool IsWhiteSpace = false; for (int i = 0; i < Value.Length; i++) { if (char.IsWhiteSpace(Value[i])) //Comparison with WhiteSpace { if (!IsWhiteSpace) //Comparison with previous Char { sbOut.Append(Value[i]); IsWhiteSpace = true; } } else { IsWhiteSpace = false; sbOut.Append(Value[i]); } } } return sbOut.ToString(); } //David S. 2013 (https://stackoverflow.com/a/16035044/2352507) public static String SingleSpacedTrim(String inString) { StringBuilder sb = new StringBuilder(); Boolean inBlanks = false; foreach (Char c in inString) { switch (c) { case '\r': case '\n': case '\t': case ' ': if (!inBlanks) { inBlanks = true; sb.Append(' '); } continue; default: inBlanks = false; sb.Append(c); break; } } return sb.ToString().Trim(); } /// <summary> /// We want to run this item with max priory to lower the odds of /// the OS from doing program context switches in the middle of our code. /// source:https://stackoverflow.com/a/16157458 /// </summary> /// <returns>random seed</returns> private static long ConfigProgramForBenchmarking() { //prevent the JIT Compiler from optimizing Fkt calls away long seed = Environment.TickCount; //use the second Core/Processor for the test Process.GetCurrentProcess().ProcessorAffinity = new IntPtr(2); //prevent "Normal" Processes from interrupting Threads Process.GetCurrentProcess().PriorityClass = ProcessPriorityClass.High; //prevent "Normal" Threads from interrupting this thread Thread.CurrentThread.Priority = ThreadPriority.Highest; return seed; }
}
基准说明：发布模式，无debugging器连接，i7处理器，平均4次运行，只testing短string
最小的解决scheme：
var regExp = / \ s + / g，newString = oldString.replace（regExp，''）;
没有办法做到这一点。 你可以试试这个：
private static readonly char[] whitespace = new char[] { ' ', '\n', '\t', '\r', '\f', '\v' }; public static string Normalize(string source) { return String.Join(" ", source.Split(whitespace, StringSplitOptions.RemoveEmptyEntries)); }
这将删除前导和尾随whitespce以及将任何内部空白折叠为单个空格字符。 如果你真的只想崩溃空间，那么使用正则expression式的解决scheme更好; 否则这个解决scheme更好。 （请参阅Jon Skeet所做的分析 。）
