Question

How to reverse the first N characters within a text file in C++

Answer 1

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

using std::cout;
using std::endl;

int main()
{
	static const char *fileName = "d:\\data.txt";
	std::string s;

	{
		std::ifstream file(fileName); 
		char ch;
		while (file.get(ch))
			s += ch; 
	}

	int N = 3;
	std::reverse(s.begin(), s.begin() + N);

	{
		std::ofstream file(fileName); 
		file << s;
	}

	return 0;
}

/*
run:

++c c
c# java php python

*/

 

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