如何将数字从一个文本文件复制到另一个文本文件但使它们成为下一个数字？

Question

I need to copy numbers from one text file and input them in another but make them the next number for example 1->2 3->4 ... 9->0 I have gotten the copying part down but cant figure out how to make one number the next.

#include <iostream>
#include <string>
#include <fstream>

using namespace std;

int main ()
{
     ifstream infile("input.txt");
     ofstream outfile("output.txt");
     string content = "";`
     int i;`

     for(i=0 ; infile.eof()!=true ; i++) // takes content 
         content += infile.get();

     i--;
     content.erase(content.end()-1);     // erase last character

     cout << i << " characters read...\n";
     infile.close();

     outfile << content;                 // output
     outfile.close();
     return 0;
}

I enter 1 2 3 4 5 and expect the output to be 2 3 4 5 6

Answer 1

You can check if an input char is a digit, then increase it, something like:

    for (i = 0; infile.eof() != true; i++)// takes content 
    {
        char currentChar = infile.get();

        if (isdigit(currentChar))
        {
            currentChar++;
        }

        content += currentChar;
    }

Answer 2

Expanding on the answer from Oded Radi,

If you want 9 to become 0 (as you described) you need to handle that, this is one way:

for (i = 0; infile.eof() != true; i++) // takes content 
{
    char currentChar = infile.get();

    if (isdigit(currentChar))
    {
        currentChar = (((currentChar - '0') + 1) % 10) + '0';
    }

    content += currentChar;
}

Answer 3

If your input is separated by whitespace, your loop can be simple:

int value;
while (input_file >> value)
{
  value = value + 1;
  output_file << value << " ";
}

Another loop could be:

int value;
while (input_file >> value)
{
    value = (value + 1) % 10;
    output << value << " ";
}

The above loop restricts the numbers from 0 to 9.