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I would like your feedback on any improvements that can be made to this Hangman game I have written in C. Specifically, improvements in terms of runtime and code organization. This game was a nice way for me to learn more about the features of the C language, specifically pointers, and thus I have heavily commented the code I have written for the purposes of learning.

Below are the source files and the CMakeLists file (which includes many runtime Clang sanitizers enabled). Alternatively, the code can be easily compiled with the following: cc *.c -o hangman && ./hangman

main.c

/**

 *                      * Hangman in C *

 * O(1) lookup using pointers to 26 letters which each have a state

 * A letter is either _ (not picked, default), or the letter itself

 * I was inspired by seeing many other Hangman implementations which

 * relied on a multiple layers of iteration, this aims to be 'simple'

 * and 'idiomatic', by using a different approach.

 *

 * @date 1/15/19

 * @author Faraz Fazli

 */



#include <stdio.h>

#include <string.h>

#include <ctype.h>

#include <stdlib.h>

#include "rng.h"

#include "utils.h"



/**

 * Use enum to replace "magic numbers" instead of #define or const

 * Ref: Practice of Programming, p.21

 */

enum {

    ALPHABET_SIZE = 26,

    TOTAL_TRIES = 10,

};



// Words the program chooses from

static char *words = {"racing", "magic", "bow", "racecar"};



int main() {

    char letters[ALPHABET_SIZE];



    // Let's set 'letters' to be composed of just _

    // This will later be changed as the user guesses

    memset(letters, '_', ALPHABET_SIZE);



    init_rng();



    // Total number of elements in our array

    size_t total_elems = len(words);



    char *word = words[rand_to(total_elems)];

    size_t word_size = strlen(word) + 1; // includes NUL character



    // Here I used 'malloc' instead of VLA

    char **word_to_guess = malloc(word_size * sizeof(word));

    size_t word_len = strlen(word); // excludes NUL



    // point each element to the appropriate letter in our array

    for (size_t i = 0; i < word_len; i++) {

        word_to_guess[i] = &letters[from_a(word[i])];

    }



    int tries = 0;

    size_t num_previous_underscores = word_len;



    print_count_underscores(word_to_guess, word_len);

    fputs("nPick a letter: ", stdout);



    // Could replace getchar() with fgets and parse each letter

    // which may serve better in the future

    int current_letter;

    while ((current_letter = getchar()) != EOF) {

        if (!isalpha(current_letter)) {

            // Simply continue - printing here causes bugs

            continue;

        }



        // convert to lower case

        current_letter = tolower(current_letter);



        // distance from 'a'

        size_t letter_pos = from_a(current_letter);



        // Letter has already been picked if it is in array

        if (letters[letter_pos] == current_letter) {

            puts("Please pick a different letter.");

            continue;

        } else {

            // Change underscore to the letter

            letters[letter_pos] = (char) current_letter;

        }



        // Finds if word still has underscores, and print word state

        size_t num_underscores = print_count_underscores(word_to_guess, word_len);



        // If letter has no correct guesses from this turn, increment tries

        if (num_underscores == num_previous_underscores) {

            tries++;

        }

        num_previous_underscores = num_underscores;



        // Win if no underscores left

        if (num_underscores == 0) {

            puts("-> YOU WIN!");

            break;

        }



        if (tries < TOTAL_TRIES) {

            printf("nTries Remaining: %dn", TOTAL_TRIES - tries);

            fputs("Pick a letter: ", stdout);

        } else {

            puts("No tries left! Game Over!");

            break;

        }

    }

    free(word_to_guess);

}

rng.c

#include "rng.h"

#include <time.h>



void init_rng(void) {

    srand((unsigned int) time(NULL));

}



size_t rand_to(size_t max) {

    return (unsigned long) rand() / (RAND_MAX / max + 1);

}

rng.h

#include <stdlib.h>



#pragma once



// Initializes random number generator

void init_rng(void);



/**

 * Helper method for Random Number Generation

 * @param max - max number

 * @return between 0 to max

 */

size_t rand_to(size_t max);

utils.c

#include <stdio.h>

#include "utils.h"



size_t len(char **arr) {

    return sizeof(arr) / sizeof(arr[0]);

}



size_t print_count_underscores(char **word_to_guess, size_t word_len) {

    size_t num_underscores = 0;

    for (size_t i = 0; i < word_len; i++) {

        printf("%c ", *word_to_guess[i]);

        if (*word_to_guess[i] == '_') {

            num_underscores++;

        }

    }

    return num_underscores;

}



size_t from_a(int letter) {

    return (size_t) abs(letter - 'a');

}

utils.h

#pragma once



#include <stdlib.h>



/**

 * Returns length of array

 * @param arr - words array

 * @return length

 */

size_t len(char **arr);



/**

 * Prints the state of each letter and counts the number of underscores

 * @param word_to_guess - word being guessed (array of pointers)

 * @param word_len - length of word (excluding NUL char)

 * @return underscore count

 */

size_t print_count_underscores(char **word_to_guess, size_t word_len);



/**

 * Returns the distance from 'a'

 * @param letter 'a' to 'z'

 * @return 0 through 25

 */

size_t from_a(int letter);