Check if the largest prime number in Prime-Daifugo can have 71 digits?

largest_dpn.cc

#include <gmpxx.h>
#include <algorithm>
#include <functional>
#include <iostream>
#include <string>
#include <vector>
using namespace std;

const char* ranks[] = {"", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13"};

// A candidate is 99998888777766665555444433332222131313131313121212121111111011010101111                                                                                                                         
int main() {
  vector<string> cards;
  for (int i = 1; i <= 13; ++i) {
    int num = (i == 1) ? 3 : ((i == 13) ? 6 : 4);
    for (int j = 0; j < num; ++j) {
      cards.push_back(ranks[i]);
    }
  }
  sort(cards.begin(), cards.end(), greater<string>());

  // Split the array into prefix part and suffix part.                                                                                                                                                            
  // Suffix part is made of "1", "10", and "11".                                                                                                                                                                  
  vector<string>::iterator suffix;
  string prefix;
  for (suffix = cards.begin(); suffix != cards.end(); ++suffix) {
    const string& c = *suffix;
    if (c == "11") {
      break;
    }
    prefix.append(c);
  }

  string largest("99998888777766665555444433332222131313131313121212121111111011010101111");
  cout << largest << "\n";
  do {
    string value(prefix);
    for (auto it = suffix; it != cards.end(); ++it)
      value.append(*it);
    int ret = mpz_probab_prime_p(mpz_class(value.c_str()).get_mpz_t(), 100);
    if (ret && value > largest) {
      cout << value << "\n";
      largest = value;
    }
  } while(next_permutation(suffix, cards.end(), greater<string>()));

  return 0;
}

largest_dpn_71dig.cc

#include <gmpxx.h>
#include <algorithm>
#include <functional>
#include <iostream>
#include <string>
#include <vector>
using namespace std;

const char* ranks[] = {"", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13"};

int main() {
  vector<string> cards;
  for (int i = 1; i <= 13; ++i) {
    int num = (i == 1) ? 3 : ((i == 13) ? 6 : 4);
    for (int j = 0; j < num; ++j) {
      cards.push_back(ranks[i]);
    }
  }
  sort(cards.begin(), cards.end(), greater<string>());
  do {
    string value;
    for (const string& c : cards)
      value += c;
    int ret = mpz_probab_prime_p(mpz_class(value.c_str()).get_mpz_t(), 100);
    if (ret) {
      cout << value << "\n";
      break;
    }
  } while(next_permutation(cards.begin(), cards.end(), greater<string>()));

  return 0;
}