/**

* Difficulty:

* Hard

*

* Desc:

* Given two words (beginWord and endWord), and a dictionary's word list,

* find all shortest transformation sequence(s) from beginWord to endWord, such that:

* 1. Only one letter can be changed at a time

* 2. Each transformed word must exist in the word list. Note that beginWord is not a transformed word.

*

* Example:

* Given:

* beginWord = "hit"

* endWord = "cog"

* wordList = ["hot","dot","dog","lot","log","cog"]

* Return

* [

* ["hit","hot","dot","dog","cog"],

* ["hit","hot","lot","log","cog"]

* ]

*

* Note:

* 1. Return an empty list if there is no such transformation sequence.

* 2. All words have the same length.

* 3. All words contain only lowercase alphabetic characters.

* 4. You may assume no duplicates in the word list.

* 5. You may assume beginWord and endWord are non-empty and are not the same.

*/

/**

* @param {string} beginWord

* @param {string} endWord

* @param {string[]} wordList

* @return {string[][]}

*/

var findLadders = function(beginWord, endWord, wordList) {

if (!beginWord || !endWord || !wordList.length) return [];

const set = new Set(wordList);

set.delete(beginWord);

const results = [];

let resultsTmp = [

[beginWord]

];

let queue = [beginWord];

let finish = false;

const loopLayer = () => {

const queueSize = queue.length;

for (let i = 0; i < queue.length; i += 1) {

set.delete(queue[i]);

}

const arr = [];

const tmp = [];

for (let z = 0; z < queueSize; z += 1) {

const word = queue.shift();

for (let i = 0; i < word.length; i += 1) {

let shouldBreak = false;

for (let j = 97; j <= 122; j += 1) {

const letter = String.fromCharCode(j);

if (letter === word[i]) continue;

const w = `${word.slice(0, i)}${letter}${word.slice(i + 1)}`;

if (set.has(w)) {

const wordArr = [...resultsTmp[z], w];

if (w === endWord) {

results.push(wordArr);

finish = true;

shouldBreak = true;

break;

}

arr.push(w);

tmp.push(wordArr);

}

}

if (shouldBreak) break;

}

}

resultsTmp = tmp;

queue = arr;

};

while (queue.length && !finish) {

loopLayer();

}

return results;

};