Automate nested Loops in C++ - c++

Question

I just got started with C++ and I'm currently trying to build an algorith that cracks passwords. I ran into a problem with nested loops for longer passwords. It currently works fine for 4 character passwords, I have to wait for a while, but it works. Is there a way to get rid of the hard coded nested loops, to make the algorithm work for more than for characters without having to copy and paste the if statements over and over again?
#include <iostream>
#include <string>
#include <ctime>
using namespace std;
const char alphanum[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!##$%^&* ";
const string pw = "0000";
bool cracked = false;
int tries = 0;
const int pwLength = pw.length();
string crack();
string guess="0";
const int maxLen = 30;
int main()
{
clock_t begin, end;
double time;
begin = clock();
string crackedPassword = crack();
end = clock();
time = double(end - begin) / (double)CLOCKS_PER_SEC;
cout << "The password is: " << crackedPassword << " The program checked a total of " << tries << " possibilites and took " << time << " seconds to crack the password!";
return 0;
}
string crack() {
int index = 0;
int repeat = 0;
while (!cracked) {
for (int i = 0; i < 71; i++) {
tries++;
guess[index] = alphanum[i];
cout << "Trying: " << guess << endl;
if (repeat > 0) {
for (int i = 0; i < 71; i++) {
tries++;
guess.push_back(alphanum[i]);
cout << "Trying: " << guess << endl;
if (repeat > 1) {
for (int i = 0; i < 71; i++) {
tries++;
guess.push_back(alphanum[i]);
cout << "Trying: " << guess << endl;
if (repeat > 2) {
for (int i = 0; i < 71; i++) {
tries++;
guess.push_back(alphanum[i]);
cout << "Trying: " << guess << endl;
if (guess == pw) {
cracked = true;
break;
}
else {
guess.pop_back();
}
}
}
if (guess == pw) {
cracked = true;
break;
}
else {
guess.pop_back();
}
}
}
if (guess == pw) {
cracked = true;
break;
}
else {
guess.pop_back();
}
}
}
if (guess == pw) {
cracked = true;
break;
}
}
repeat++;
}
return guess;
}