My Wordle Solver (Probably Buggy)

wordle.c

// Brian Chrzanowski
// 2022-06-05 02:04:34
//
// My Wordle Solver.
//
// I'd been meaning to write one of these for a while. Basically, we slurp up the entire wordlist,
// and we literally just throw away words if they don't match the Worlde word.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <ctype.h>
#include <limits.h>

#define DICTFILE "/usr/share/dict/american-english"
#define LISTLIM  (1 << 20) // seems big enough :p
#define WORDLELEN (5)

char *WORDLIST[LISTLIM];
int TOTALWORDS = 0;

void strtolower(char *s)
{
	for (;*s;s++) *s = tolower(*s);
}

void mktab(int *tab, char c, char *w, char *r)
{
	for (int i = 0; i < WORDLELEN; i++) {
		if (r == NULL || r[i] == c)
			tab[w[i] - 'a']++;
	}
}

int chkwon(char *s)
{
	while (*s) {
		if (*s != 'g')
			return 0;
		s++;
	}
	return 1;
}

int xmatch(char *candidate, char *word, char *result)
{
	int tab[26];

	memset(&tab, 0, sizeof tab);
	mktab(tab, 'x', word, result);

	for (int i = 0; i < WORDLELEN; i++) {
		if (tab[candidate[i] - 'a'] > 0)
			return 1;
	}

	return 0;
}

int gmatch(char *candidate, char *word, char *result)
{
	int i;

	for (i = 0; i < 5; i++)
		if (result[i] == 'g' && candidate[i] != word[i])
			return 0;

	return 1;
}

int ymatch(char *candidate, char *word, char *result)
{
#define LETTERS 26
	int yellows[LETTERS];
	int clettrs[LETTERS];

	memset(&yellows, 0, sizeof yellows);
	memset(&clettrs, 0, sizeof clettrs);

	mktab(yellows, 'y', word, result);
	mktab(clettrs, 'y', candidate, NULL);

	for (int i = 0; i < LETTERS; i++) {
		if (0 < yellows[i] && !(clettrs[i] <= yellows[i]))
			return 0;
	}

	return 1;
}

void crunchlist(char *word, char *result)
{
	for (int i = 0; i < TOTALWORDS; i++) {
		if (WORDLIST[i] == NULL)
			continue;

		if (xmatch(WORDLIST[i], word, result) || !(gmatch(WORDLIST[i], word, result) && ymatch(WORDLIST[i], word, result))) {
			free(WORDLIST[i]);
			WORDLIST[i] = NULL;
		}
	}
}

void printentries(int n)
{
	for (int i = 0; i < TOTALWORDS && n; i++) {
		if (WORDLIST[i] != NULL) {
			printf("%s\n", WORDLIST[i]);
			n--;
		}
	}
}

int main(int argc, char **argv)
{
	FILE *fp;
	char buf[1024];
	int i;

	memset(WORDLIST, 0, sizeof WORDLIST);

	fp = fopen(DICTFILE, "rb");
	if (!fp) {
		fprintf(stderr, "couldn't open dictionary file!\n");
		return 1;
	}

	for (i = 0; i < LISTLIM && buf == fgets(buf, sizeof buf, fp); i++) {
		buf[strlen(buf) - 1] = 0;

		if (strlen(buf) != 5) // wordle words are 5 chars long
			continue;

#define CHARTEST(x) !(isalpha((x)) && islower((x)))

		if (CHARTEST(buf[0])) continue;
		if (CHARTEST(buf[1])) continue;
		if (CHARTEST(buf[2])) continue;
		if (CHARTEST(buf[3])) continue;
		if (CHARTEST(buf[4])) continue;

		assert(i < LISTLIM);

		WORDLIST[TOTALWORDS++] = strdup(buf);
	}

	fclose(fp);

#if 0
	for (i = 0; i < TOTALWORDS; i++) {
		printf("%s\n", WORDLIST[i]);
	}
#endif

	char word[8];
	char result[8];
	int win_state, guess;

	// As we ask the user for guesses and board states, we begin to filter the list to appropriate
	// words that could be used in the future, assuming all input information is correct. To do
	// this, we actually just free the item in the list and set the pointer to NULL, if it violates
	// any of the information that we've got.

	for (win_state = guess = 0; guess < 6 && !win_state; guess++) {
		printf("Guess > ");
		fgets(word, sizeof word, stdin);
		word[strlen(word) - 1] = 0;
		strtolower(word);

		printf("State > ");
		fgets(result, sizeof result, stdin);
		result[strlen(result) - 1] = 0;
		strtolower(result);

		win_state = chkwon(result);
		if (win_state)
			break;

		crunchlist(word, result);

		printentries(10); // we literally don't do anything special to print a diverse set of guesses
	}

	if (win_state) {
		printf("CONGRATS, YOU CHEATED!\n");
	} else {
		printf("You couldn't even win without cheating? Pathetic.\n");
	}

	return 0;
}