Array changing its first letter without reason - c

Question

I'm making a hangman and everything works fine if you win, but if you lose it doesn't print the word it was.
I was debugging it and I found that in one of the last iterations the first character is changed to '\000' so that is why it doesn't print, but I don't understand why because there is no line where the array word is changed.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#define VOCABULARY_SIZE 8
#define MAX_STRING 32
#define MAX_GUESS 6
int random_number(int a, int b)
{
return a + rand() % (b - a + 1);
}
int main()
{
//random word selection
srand((unsigned)time(NULL));
const char VOCABULARY[VOCABULARY_SIZE][MAX_STRING] = {"vehicle", "building", "shirt", "pencil", "batman", "dromedary", "peach", "hangman"};
char word[MAX_STRING];
int i;
i = random_number(0, VOCABULARY_SIZE - 1);
strcpy(word, VOCABULARY[i]);
//user word
int guesses = 0, length = strlen(word);
char letters[MAX_GUESS+1];
char input[MAX_STRING];
char temp_char;
char temp_input[MAX_STRING];
do
{
printf("\nYour entered letters are: ");
printf("%s", letters);
printf("\nYour letters found are: ");
for (int j = 0; j < length; j++)
{
if (word[j] == input[j])
{
printf("%c", word[j]);
}
else
{
printf("_");
}
}
printf("\n%d-letter word. %d out of %d failures. Enter a letter: ", length, guesses, MAX_GUESS);
scanf(" %c", &temp_char);
letters[guesses] = temp_char;
letters[guesses+1] = '\0';
for (int j = 0; j < length; j++)
{
if (word[j] == temp_char)
{
input[j] = word[j];
}
}
guesses++;
printf("\nWhat is the word to guess? ");
scanf(" %s", temp_input);
} while ((strcmp(input, word) != 0 && strcmp(temp_input, word) != 0) && guesses <= MAX_GUESS);
if (strcmp(input, word) == 0 || strcmp(temp_input, word) == 0)
{
printf("\nCongratulations, the word was %s!", word);
}
else
{
printf("\nBetter luck next time... The word was %s", word);
}
}

Answer 1

You're writing to letters out of bounds
char letters[MAX_GUESS+1];
int guesses = 0;
do {
//...
letters[guesses+1] = '\0'; // OOPS
//...
guesses++;
//...
} while (... && guesses <= MAX_GUESS);

Answer 2

Nicely written code, but errors in string management.
Initialize
First time printf("%s", letters); called, letters[] is junk. Initialize it.
// char letters[MAX_GUESS + 1];
char letters[MAX_GUESS + 1] = { 0 };
Too many guess
Off by 1, lower limit.
// ... && guesses <= MAX_GUESS);
... && guesses < MAX_GUESS);
Missing '\0'
strcmp(input, word) uses input as a string, yet it lacks a null character.
Flush
Best to insure output is seen before asking for input.
fflush(stdout); // add
scanf(" %c", &temp_char);
fflush(stdout); // add
scanf(" %s", temp_input);
Unbounded input
scanf(" %s", temp_input); is worse than gets(). Research fgets().
Perhaps more issues.