istreambuf_iterator

#include <set>
#include <stdio.h>
#include <iostream>
#include <istream>
#include <fstream>
#include <iterator>
using namespace std;

int main()
{
    ifstream inputFile("1.txt");
    string fileData((istreambuf_iterator<char>(inputFile)),
    istreambuf_iterator<char>());
    cout<<fileData<<endl;
    return 0;
}