/**
 * https://leetcode.com/problems/word-ladder/
 * Time O(ROWS * COLS) | Space O(ROWS * COLS)
 * @param {string} beginWord
 * @param {string} endWord
 * @param {string[]} wordList
 * @return {number}
 */
var ladderLength = function (beginWord, endWord, wordList) {
    const [queue, wordSet, seen] = [
        new Queue([[beginWord, 1]]),
        new Set(wordList),
        new Set([beginWord]),
    ];

    return bfs(
        queue,
        wordSet,
        seen,
        endWord,
    ); /* Time O(ROWS * COLS) | Space O(ROWS * COLS) */
};

const bfs = (queue, wordSet, seen, endWord) => {
    while (!queue.isEmpty()) {
        for (let i = queue.size() - 1; 0 <= i; i--) {
            const [word, depth] = queue.dequeue();

            const isTarget = word === endWord;
            if (isTarget) return depth;

            transform(queue, wordSet, seen, word, depth);
        }
    }

    return 0;
};

const transform = (queue, wordSet, seen, word, depth) => {
    for (const index in word) {
        for (const char of 'abcdefghijklmnopqrstuvwxyz') {
            const neighbor = getNeighbor(word, index, char);

            const hasSeen = !wordSet.has(neighbor) || seen.has(neighbor);
            if (hasSeen) continue;

            queue.enqueue([neighbor, depth + 1]);
            seen.add(neighbor);
        }
    }
};

const getNeighbor = (word, index, char) => {
    const neighbor = word.split('');

    neighbor[index] = char;

    return neighbor.join('');
};