Enigma C++

gistfile1.cpp

#include <iostream>
#include <cstring>
using namespace std;

char alpha[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char rotors[3][27] = 
{
  "EKMFLGDQVZNTOWYHXUSPAIBRCJ",
  "AJDKSIRUXBLHWTMCQGZNPYFVOE",
  "BDFHJLCPRTXVZNYEIWGAKMUSQO"
};
char reflector[] = "YRUHQSLDPXNGOKMIEBFZCWVJAT";
char key[] = "ABC";


long mod26(long a)
{
  return (a%26+26)%26;
}

int li (char l)
{
  return l - 'A';
}

int indexof (char* array, int find)
{
  return strchr(array, find) - array;
}

string crypt (const char *ct)
{
  int L = li(key[0]);
  int M = li(key[1]);
  int R = li(key[2]);

  string output;

  for ( int x = 0; x < strlen(ct) ; x++ ) {
    int ct_letter = li(ct[x]);

    R = mod26(R + 1);

    char a = rotors[2][mod26(R + ct_letter)];
    char b = rotors[1][mod26(M + li(a) - R)];
    char c = rotors[0][mod26(L + li(b) - M)];

    char ref = reflector[mod26(li(c) - L)];

    int d = mod26(indexof(rotors[0], alpha[mod26(li(ref) + L)]) - L);
    int e = mod26(indexof(rotors[1], alpha[mod26(d + M)]) - M);
    char f = alpha[mod26(indexof(rotors[2], alpha[mod26(e + R)]) - R)];

    output += f;
  }

  return output;
}

int main ()
{
  // for ( int i = 0; i < 1000000; i++) {
  cout << crypt ("PZUFWDSASJGQGNRMAEODZJXQQKHSYGVUSGSU");
  // }
  
  return 0;
}

Quick question. Using the algorithm you have there, why does it refuse to work if you randomise letter positions in rotors?