Cracker

#include <stdio.h>
#include <string.h>
#include <time.h>

int incrementPassword(char*, int);
void initPassword(char*);
int indexOf(char, int);

const char* PASSWORD_CHARS = "abcdefghijklmnopqrstuvwxyz";
const int PASSWORD_LENGTH = 8;
const int DISPLAY = 0;

int main(){
    char password[PASSWORD_LENGTH];
    int passwordCharPoolSize = strlen(PASSWORD_CHARS);
    clock_t start, stop;

    printf("Starting evaluation of %d-character length password, with %d characters\n",
        PASSWORD_LENGTH, passwordCharPoolSize);
    start = clock();

    while(incrementPassword(password, passwordCharPoolSize));

    stop = clock();
    double executionTime = (double)(stop - start) / CLOCKS_PER_SEC;

    printf("Execution time: %lf seconds\n", executionTime);

    return 0;
}

// The password keeps track of itself. In other words, the next
// password can be derived from the previous one
int incrementPassword(char* password, int PASSWORD_CHARS_LEN){
    int i = 0;
    while(i < PASSWORD_LENGTH){
        if(i == PASSWORD_LENGTH && password[0] == PASSWORD_CHARS[PASSWORD_CHARS_LEN - 1]){
            // The loop is over; the last character has been incremented
            break;
        }
        char currentChar = password[PASSWORD_LENGTH - 1 - i];
        if(currentChar == PASSWORD_CHARS[PASSWORD_CHARS_LEN - 1]){
            password[PASSWORD_LENGTH - 1 - i] = PASSWORD_CHARS[0];
            i++;
        }
        else{
            char nextChar= PASSWORD_CHARS[indexOf(currentChar, PASSWORD_CHARS_LEN) + 1];
            password[PASSWORD_LENGTH - 1 - i] = nextChar;
            if(DISPLAY){
                printf("%s\n", password);
            }
            return 1; // Keep the main loop running
        }
    }
    // Stops the main loop by returning false
    return 0;
}

// Initializes a password to the first character of the character pool
void initPassword(char* password){
    int i = 0;
    while(i < PASSWORD_LENGTH){
        password[i] = PASSWORD_CHARS[0];
        i++;
    }
}

// Since the pool of characters isn't in order, this finds the
// index of a given character
int indexOf(char c, int PASSWORD_CHARS_LEN){
    int i = 0;
    while(i < PASSWORD_CHARS_LEN){
        if(PASSWORD_CHARS[i] == c){
            return i;
        }
        i++;
    }
    // Didn't find it
    return -1;
}