计算一个字符在文本文件中出现的次数

本文关键字：文件 文本 字符 一个 计算 | 更新日期: 2023-09-27 18:27:34

我正在学习C#，我想计算一个字符在文本文件中出现的次数。用户输入文本文件的路径和要搜索的字符。程序当前找不到任何字符。我做错了什么？这是代码：

    public static void Main(string[] args)
    {
        string fileName;
        fileName = readInput("Please enter the path to the file: ");
        StreamReader fromFile = new StreamReader(fileName);
        string line;
        while ((line = fromFile.ReadLine()) != null)
        {
            Console.WriteLine(line);
        }
        int count = 0;
        char search;
        search = readSearch("Please enter the character you want to search for: ");
        while ((line = fromFile.ReadLine()) != null)
        {
            foreach (char letter in line)
            {
                if (search == letter)
                {
                    count ++;
                }
            }
        }
        Console.WriteLine("{0} was found {1} time(s).", search, count);
        Console.ReadLine();
        fromFile.Close();
        Console.ReadLine();
    }
    private static string readInput(string questionPath)
    {
        Console.Write(questionPath);
        string input = Console.ReadLine();
        return input;
    }
    private static char readSearch(string questionSearch)
    {
        Console.Write(questionSearch);
        char input = Convert.ToChar(Console.Read());
        return input;
    }
}

计算一个字符在文本文件中出现的次数

看起来是在计算匹配的字符之前将文件写入屏幕。这样做时，您可以将StreamReader移动到文件的末尾，而不重置它。每次重置读取器（并使用using）：

StreamReader fromFile;
using(fromFile = new StreamReader(fileName))
{
     string line;
     while ((line = fromFile.ReadLine()) != null)
     {
         Console.WriteLine(line);
     }
}
int count = 0;
char search;
search = readSearch("Please enter the character you want to search for: ");
using(fromFile = new StreamReader(fileName))
{
     while ((line = fromFile.ReadLine()) != null)
     {
        //....
     }
}

或者您可以先将文件读入内存。

问题是您已经通读了整个流。一个简单的修复方法是从头开始重新启动读取。这可以通过在开始计数操作之前执行以下操作来完成：

        fromFile.BaseStream.Seek(0, SeekOrigin.Begin);

作为附加信息，您可以将计数操作替换为LINQ语句。更换：

            foreach (char letter in line)
            {
                if (search == letter)
                {
                    count++;
                }
            }

带有：

            count += line.Count(letter => search == letter);

此代码将打开一个文件，计算其中每个字符的数量，并将总数输出到另一个文件。

            if (File.Exists(charCountFileName)) File.Delete(charCountFileName);
            SortedDictionary<ushort, int> charsDict = new SortedDictionary<ushort, int>();
            using (StreamReader r = new StreamReader(inputFileName))
            {
                char[] buffer = new char[1024];
                int read;
                while ((read = r.ReadBlock(buffer, 0, buffer.Length)) > 0)
                {
                    for (int i = 0; i < read; i++)
                    {
                        if (!charsDict.ContainsKey((ushort)buffer[i]))
                        {
                            charsDict.Add((ushort)buffer[i], 1);
                        }
                        else
                            charsDict[(ushort)buffer[i]]++;
                    }
                }
            }           
            using (StreamWriter file = new StreamWriter(new FileStream(charCountFileName, FileMode.Create), Encoding.UTF8))
                foreach (var entry in charsDict)
                    file.WriteLine("{0}'t{1}'t{2}", entry.Key, Convert.ToChar(entry.Key), entry.Value);
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