c# 使用正则表达式将多个.txt 文件合并为一个.txt 文件

Question

I have a huge problem. I need to merge two.txt files into third one, each line by line. I need before that to each line trim end of first file last two characters and to trim first two characters of second file. Before merging I have to find matches on the end of first file with beginning of second file. Namely, first file should be left part of sentence, second file right part of sentence. Example:

file 1 content (first line):

A very long ago, our Milky Way had a truly eventful life: between

file 2 content (first line):

eventful life: between about 13 and 8 billion years ago, it lived hard and fast, merging with other galaxies and consuming a lot of hydrogen to form stars.

file 3 content should be (first line):

A very long ago, our Milky Way had a truly eventful life: between about 13 and 8 billion years ago, it lived hard and fast, merging with other galaxies and consuming a lot of hydrogen to form stars.

So, in short, I have to in this example of text to trim "eventful life: between " from second file and to trim last two of first file and last two of second and to finally merge texts from first and second file into third. Thanks in advance!

namespace ConsoleApplication1

class Program
    {
        
static void Main()
        {
            
            
                
                string[] readleft = File.ReadAllLines(@"C:\Users\J\Desktop\files\left.txt");
                string[] readright = File.ReadAllLines(@"C:\Users\J\Desktop\files\right.txt");
                using (StreamReader swo = new StreamReader(@"C:\Users\J\Desktop\files\left.txt"))
                {
                    //left file is first, second is right and third is output
                    using (StreamReader swot = new StreamReader(@"C:\Users\J\Desktop\files\right.txt"))
                    { 
                        for (int x = 0; x < readleft.Length || x < readright.Length; x++)
                        {
                            Console.WriteLine("{0}{1}",swo.ReadLine(),swot.ReadLine());
                            Match m = Regex.Match(swo.ToString(), swot.ToString());
                            if(m.Success)
                                Console.WriteLine("Found '{0}' at position '{1}'", m.Value.ToString(), m.Index);
                        }
                    }
                }
}
    }

BTW, why does it showing me "System.IO.StreamReader" instead of matching?

Answer 1

Here's a simple way that it's easy to understand.

var left = "A very long ago, our Milky Way had a truly eventful life: between";
var right = "eventful life: between about 13 and 8 billion years ago, it lived hard and fast, merging with other galaxies and consuming a lot of hydrogen to form stars.";

int common = 0;
for(int i = 1; i < Math.Min(left.Length, right.Length); i++)//Please note that a binary search would be much faster
{
    var partToCheck = right.Substring(0,i);
    if(left.EndsWith(partToCheck))
    {
        common = i;
        Console.WriteLine($"Common part: '{right.Substring(0,i)}'");
        break;
    }
}
var merged = left + right.Substring(common);

This prints

Common part: 'eventful life: between'