problem013.cpp

// Compile with the following command:
// g++ problem013.cpp -lgmpxx -lgmp

#include <gmpxx.h>

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

int main(int argc, char* argv[])
{
 if (argc < 2) {
 std::cout << "Usage: " << argv[0] << " <input>\n";
 return 0;
 }
 std::ifstream file(argv[1]);
 if (!file.is_open()) {
 std::cerr << "Cannot open " << argv[1] << '\n';
 return EXIT_FAILURE;
 }
 mpz_class sum;
 std::string line;
 while (std::getline(file, line)) {
 sum += mpz_class(line);
 }
 std::string ans(sum.get_str(), 0, 10);
 std::cout << "Answer: " << ans << '\n';
 return 0;
}