0271-encode-and-decode-strings.js

/**
 * String - Delimiter
 * Time O(N) | Space O(1)
 * https://leetcode.com/problems/encode-and-decode-strings/
 * @param {string[]} strs
 * @return {string}
 */
var encode = (strs) => {
    return strs
        .map(
            (str) => `${str.length}#${str}`,
        ) /* Time O(N) | Ignore Auxillary Space O(N) */
        .join(''); /* Time O(N) | Ignore Auxillary Space O(N) */
};

/**
 * String - Delimiter
 * Time O(N * K) | Space O(N)
 * https://leetcode.com/problems/encode-and-decode-strings/
 * @param {string} str
 * @return {string[]}
 */
var decode = (str, index = 0, decodedWords = []) => {
    while (index < str.length) {
        /* Time O(N) */
        const { nextIndex, word } = delimitWord(
            str,
            index,
        ); /* Time O(K) | Ignore Auxillary Space Space (K) */

        decodedWords.push(
            word,
        ); /*           | Ignore Auxillary Space O(N * K ) */
        index = nextIndex;
    }

    return decodedWords;
};

const delimitWord = (str, index) => {
    const delimiter = str.indexOf('#', index); /* Time O(K) */
    const length = Number(str.slice(index, delimiter)); /* Time O(K) */
    const [start, end] = [delimiter + 1, delimiter + length + 1];
    const word = str.slice(
        start,
        end,
    ); /* Time O(K) | Ignore Auxillary Space O(K) */

    return {
        nextIndex: end,
        word,
    };
};

/**
 * Non-ASCII Delimiter - Ignore Auxiliary Space
 * Time O(N) | Space O(1)
 * https://leetcode.com/problems/encode-and-decode-strings/
 * @param {string[]} strs
 * @return {string}
 */
var encode = (strs, nonASCIICode = String.fromCharCode(257)) => {
    return strs.join(
        nonASCIICode,
    ); /* Time O(N) | Ignore Auxillary Space O(N) */
};

/**
 * Non-ASCII Delimiter - Ignore Auxiliary Space
 * Time O(N) | Space O(1)
 * https://leetcode.com/problems/encode-and-decode-strings/
 * @param {string[]} strs
 * @return {string}
 */
var decode = (strs, nonASCIICode = String.fromCharCode(257)) => {
    return strs.split(
        nonASCIICode,
    ); /* Time O(N) | Ignore Auxillary Space O(N) */
};

/**
 * Chunk Transfer Encoding
 * Time O(N) | Space O(1)
 * https://leetcode.com/problems/encode-and-decode-strings/
 * @param {string[]} strs
 * @return {string}
 */
var encode = (strs, sb = []) => {
    for (const str of strs) {
        /* Time O(N) */
        const code = getCode(str); /* Time O(1) */
        const encoding = `${code}${str}`;

        sb.push(encoding);
    }

    return sb.join(''); /* Time O(N) | Ignore Auxillary Space O(N) */
};

const getCode = (str) => str.length.toString(2).padStart(8, '0');

/**
 * Chunk Transfer Encoding
 * Time O(N) | Space O(1)
 * https://leetcode.com/problems/encode-and-decode-strings/
 * @param {string} str
 * @return {string[]}
 */
var decode = (str, output = []) => {
    for (
        let left = 0, right = left + 8, length = 0;
        left < str.length;
        left = right + length, right = left + 8
    ) {
        /* Time O(N) */
        const countString = str.slice(
            left,
            right,
        ); /*           | Ignore Auxillary Space O(K) */
        length = parseInt(countString, 2);

        const decoding = str.slice(
            right,
            right + length,
        ); /* Time O(K) | Ignore Auxillary Space O(N * K) */
        output.push(decoding); /*           | Ignore Auxillary Space O(N * K) */
    }

    return output;
};