generate-all-string-combinations.c

//
//  main.c
//  StringGenerator
//
//  Created by William Shepherd on 11/8/17.
//  Copyright © 2017 William Shepherd. All rights reserved.
//

#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <string.h>

const char *ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
const int ALPHABET_SIZE = 52;

void genStr(int k);
void genStrHelper(char *seed, int index);
char *strRep(char c, int n);

int main(int argc, const char * argv[])
{
    genStr(5);
    
    return 0;
}

void genStr(int k)
{
    char *seedStr;
    
    for (int i = 1; i <= k; i++)
    {
        for (int j = 0; j < ALPHABET_SIZE; j++)
        {
            seedStr = strRep(ALPHABET[j], i);
            
//            printf("%s\n", seedStr);
            genStrHelper(seedStr, 1);
            free(seedStr);
        }
    }
}

void genStrHelper(char *seed, int index)
{
    long seed_length = strlen(seed);
    
    if(seed == NULL || seed_length < 2 || index >= seed_length)
        return;
    
    int currCharIdx = seed[index] - ALPHABET[0];
    
    for (int i = 0; i < ALPHABET_SIZE; i++)
    {
        seed[index] = ALPHABET[(currCharIdx + i + 1) % ALPHABET_SIZE];
        
//        printf("%s\n", seed);
        genStrHelper(seed, index + 1);
    }
}

char *strRep(char c, int n)
{
    char *result = (char *)malloc(sizeof(char) * (n + 1));
    
    for (int i = 0; i < n; i++)
        result[i] = c;
    result[n] = '\0';
    
    return result;
}