使用特殊情況獲得前140個字符串的字符串

Question

我有一個字符串，它的長度限制為140個字符。 通常，我的代碼中有超過140個。 字符串是以這種格式設置的值：Mxxxx其中x可以是任何數字，並且它沒有嚴格的長度。 所以我可以擁有M1或者我也可以擁有M281。

如果string超過140個字符，我想先取140，但如果最后一個打破了一半，我根本不想把它放在我的字符串中。

不過，我需要在一些局部變量中保存下半部分。

例如，假設這是字符串

"M5903, M6169, M6753, M619, M6169, M6753, M6919, M6169, M6753, M919, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M919, M6169, M6753, M6919, M669, M6753, M6919, M69, M6753, M6919, M6169, M63, M6919, M6169, M6753, M6919, M619, M653, M6919, M66, M6753, M19, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M619"

讓我們說這是前140個字符：

"M5903, M6169, M6753, M619, M6169, M6753, M6919, M6169, M6753, M919, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M919, M6169, M6753, M6919, M669, M6753, M6919, M69, M6753, M6919, M6169, M63, M69"

最后一個值是M6919但它M6919 M69和19 。

最有效的說法是：如果它超過140則拆分，但如果新字符串中的最后一個值被吐出，則將其從字符串的第一部分移除，並將其與原始字符串的其余部分一起放入其他字符串值中。

可能有很多方法可以實現這一目標。 我可以使用if或switch / case循環，並說如果第二個字符串的第一個字母不是'M'，我知道該值被拆分，我應該從第一個字符串中刪除它，但是有人有更清晰的解決方案嗎？

private static string CreateSettlmentStringsForUnstructuredField(string settlementsString)
{
    string returnSettlementsString = settlementsString.Replace(", ", " ");

    if (returnSettlementsString.Length > 140)
    {
        returnSettlementsString.Substring(0, 140);
        /*if returnSettlementsString was spitted in two in a way 
          that last value was broken in two parts, take that value 
          out of returnSettlementStrings and put it in some new 
          string value with the other half of the string.*/
    }
    return returnSettlementsString;
} 

Answer 1

這樣的事情可能有用：

string result;
if (input.Length > 140)
{
    result = new string(input.Take(140).ToArray());
    if (input[140] != ',') // will ensure that we don´t omit the last complete word if the 140eth character is a comma
        result = result.Substring(0, result.LastIndexOf(','));
} 
else result = input;

如果總長度更大，它只需要前140個字符。 然后它搜索逗號的最后一個索引並獲取所有字符， 直到這個逗號。

Answer 2

最好的辦法是將字符串拆分為“單詞”，然后使用字符串生成器重新組合它們。 未經測試的原始代碼看起來像;

public IEnumerable<string> SplitSettlementStrings(string settlementsString) 
{
    var sb = new StringBuilder();
    foreach(var word in WordsFrom(settlementsString))
    {
        var extraFragment = $"{word}, ";
        if (sb.Length + extraFragment < 140) {
        sb.Append(extraFragment);
    }
    else
    {
        // we'd overflow the 140 char limit, so return this fragment and continue;
        yield return sb.ToString();
        sb = new StringBuilder();
    }

    if (sb.Length > 0) {
        // we may have content left in the string builder
        yield return sb.ToString();
    }
}

你需要使用這樣的東西來分割單詞;

 public IEnumerable<string> WordsFrom(string settlementsString) 
 {
    // split on commas, then trim to remove whitespace;
    return settlementsString.split(',').Select(x => x.Trim()).Where(x => x.Length > 0);
 }

你會像這樣使用整體;

 var settlementStringsIn140CharLenghts = SplitSettlementStrings("M234, M456, M452 ...").ToArray()

編輯

old-skool .net版本看起來像這樣;

public ICollection<string> SplitSettlementStrings(string settlementsString) 
{
    List<string> results = new List<string>();
    StringBuilder sb = new StringBuilder();
    foreach(string word in WordsFrom(settlementsString))
    {
        string extraFragment = word + ", ";
        if (sb.Length + extraFragment < 140) {
           sb.Append(extraFragment);
        }
    }
    else
    {
        // we'd overflow the 140 char limit, so return this fragment and continue;
        results.Add(sb.ToString());
        sb = new StringBuilder();
    }

    if (sb.Length > 0) {
        // we may have content left in the string builder
        resuls.Add(sb.ToString());
    }
}

 public ICollection<string> WordsFrom(string settlementsString) 
 {
    // split on commas, then trim to remove whitespace;
    string[] fragments = settlementsString.split(',');
    List<string> result = new List<string>();
    foreach(string fragment in fragments) 
    {
        var candidate = fragment.Trim();
        if (candidate.Length > 0) 
        {
            result.Add(candidate);
        }
    } 
    return result;
 }

Answer 3

這樣的事情應該有效：

string test = "M5903, M6169, M6753, M619, M6169, M6753, M6919, M6169, M6753, M919, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M919, M6169, M6753, M6919, M669, M6753, M6919, M69, M6753, M6919, M6169, M63, M6919, M6169, M6753, M6919, M619, M653, M6919, M66, M6753, M19, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M619";

if (test.Length > 140)
    if (test[140] != ',' && test[140] != ' ') // Last entry was split?
        test = test.Substring(0, test.LastIndexOf(',', 139)); // Take up to but not including the last ','
    else
        test = test.Substring(0, 139);

Console.WriteLine(test);

Answer 4

我的看法，只是為了好玩：

var ssplit = theString.Replace(", ", "#").Split('#');       
var sb = new StringBuilder();
for(int i = 0; i < ssplit.Length; i++)
{
    if(sb.Length + ssplit[i].Length > 138) // 140 minus the ", "
        break;
    if(sb.Length > 0) sb.Append(", ");
    sb.Append(ssplit[i]);
}

在這里，我將字符串拆分為Mxxx部分。 然后我遍歷這些部分，直到下一部分溢出140（或138，因為它需要在計數中包含", "分隔符）

看到它在行動

Answer 5

如果您不想將字符串拆分為列表，我會執行以下操作：

string myString = "M19, M42........";
string result;
int index = 141;

do
{
    //Decrement index to reduce the substring size
    index--;

    //Make the result the new length substring
    result = myString.Substring(0, index);

}while (myString[index] != ','); //Check if our result contains a comma as the next char to check if we're at the end of an entry

因此，您基本上只是將原始字符串子串到140，檢查位置141處的字符是否為逗號，表示“干凈”剪切。 如果沒有，它將在139處子串，檢查140是否有逗號等。

Answer 6

這是一個解決方案。 它從第141個字符開始向后處理字符串。

public static string Normalize(string input, int length)
{
    var terminators = new[] { ',', ' ' };
    if (input.Length <= length + 1)
        return input;

    int i = length + 1;
    while (!terminators.Contains(input[i]) && i > 0)
        i = i - 1;

    return input.Substring(0, i).TrimEnd(' ', ',');
}

Normalize(settlementsString, 140);

Answer 7

由於新字符串的持續內存分配，可能不是性能最敏感的解決方案，但它確實聽起來像某種類型的一次性原始數據輸入。 我們可以選擇從輸入中刪除“令牌”，而我們有超過140個字符：

const string separator = ", ";

while (input.Length > 140)
{
     int delStartIndex = input.LastIndexOf(separator);
     int delLength = input.Length - delStartIndex;

     input = input.Remove(delStartIndex, delLength);
}

更加注重性能的方法是為子string[]創建一個IEnumerable<string>或string[]形式，並在加入它們之前計算它們的總長度。 有點像這樣：

const string separator = ", ";
var splitInput = input.Split(separator.ToCharArray(), StringSplitOptions.RemoveEmptyEntries);

var length = splitInput[0].Length;
var targetIndex = 1;

for (targetIndex = 1; length <= 140; targetIndex++)
    length += separator.Length + splitInput[targetIndex].Length;

if (length > 140)
    targetIndex--;

var splitOutput = new string[targetIndex];
Array.Copy(splitInput, 0, splitOutput, 0, targetIndex);

var output = string.Join(separator, splitOutput);

我們甚至可以做一個很好的擴展方法：

public static class StringUtils
{
    public static string TrimToLength(this string input, string separator, int targetLength)
    {
        var splitInput = input.Split(separator.ToCharArray(), StringSplitOptions.RemoveEmptyEntries);

        var length = splitInput[0].Length;
        var targetIndex = 1;

        for (targetIndex = 1; length <= targetLength; targetIndex++)
            length += separator.Length + splitInput[targetIndex].Length;

        if (length > targetLength)
            targetIndex--;

        var splitOutput = new string[targetIndex];
        Array.Copy(splitInput, 0, splitOutput, 0, targetIndex);

        return string.Join(separator, splitOutput);
    }
}

並稱之為：

input.TrimToLength(", ", 140);

要么：

input.TrimToLength(separator: ", ", targetLength:140);

Answer 8

我用這個：

static string FirstN(string s, int n = 140)
{
    if (string.IsNullOrEmpty(s) || s.Length <= n) return s;
    while (n > 0 && s[n] != ' ' && s[n] != ',') n--;
    return s.Substring(0, n);
}

工作測試示例代碼（帶注釋輸出）：

using System;
namespace ConsoleApplication1
{
    class Program
    {
        static string FirstN(string s, int n = 140)
        {
            if (string.IsNullOrEmpty(s) || s.Length <= n) return s;
            while (n > 0 && s[n] != ' ' && s[n] != ',') n--;
            return s.Substring(0, n);
        }
        static void Main(string[] args)
        {
            var s = FirstN("M5903, M6169, M6753, M619, M6169, M6753, M6919, M6169, M6753, M919, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M919, M6169, M6753, M6919, M669, M6753, M6919, M69, M6753, M6919, M6169, M63, M6919, M6169, M6753, M6919, M619, M653, M6919, M66, M6753, M19, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M619");

            Console.WriteLine(s.Length); // 136
            Console.WriteLine(s);  //M5903, M6169, M6753, M619, M6169, M6753, M6919, M6169, M6753, M919, M6169, M6753, M6919, M6169, M6753, M6919, M6169, M6753, M919, M6169,
        }
    }
}

我希望這有幫助。