Problem accessing the last element of the array

Question

I've decided to implement the load function using trie, which I've defined as

    typdef struct trie
    {
        struct trie letters[27];
        bool isWord;
    }trie;

then later, when I try to access the last element, i.e, letters[27] as per

    if (c == 96)
    {
         trav->letters[27] = malloc(sizeof(trie));
         trav = trav->letters[27];
    }

The compiler throws an error: array index 27 is past the end of the array (which contains 27 elements) Now, changing the definition of struct to 28 solves the problem, obviously, but when we define an array as - int array[x], doesn't it contain elements from 0 to x? That's how it works elsewhere I think, or am I doing something wrong? Thanks

Answer 1

If an array contains 27 elements and the first element is index 0, then the last element is index 26. The last index is always one less than the number of elements, because indexes start at 0.