encodeAndDecodeStrings.js

/*
https://leetcode.com/problems/encode-and-decode-strings/description

Description
Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings.

Please implement encode and decode

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Example 1:
Input: ["lint","code","love","you"]
Output: ["lint","code","love","you"]
Explanation:
One possible encode method is: "lint:;code:;love:;you"

Example 2:
Input: ["we", "say", ":", "yes"]
Output: ["we", "say", ":", "yes"]
Explanation:
One possible encode method is: "we:;say:;:::;yes"
*/

const DELIMITER = "##BREAK##";

const encode = (strs) => {
    let nums = "";
    let concattedStr = "";
    for (let i = 0; i < strs.length; i++) {
        const str = strs[i];
        nums += `${str.length}`;
        if (i < strs.length - 1) {
            nums += ",";
        }
        concattedStr += str;
    }

    return nums + DELIMITER + concattedStr;
};

const decode = (str) => {
    const [nums, strs] = str.split(DELIMITER);
    const result = [];

    const numsArr = nums.split(",");
    let strIndex = 0;
    for (let i = 0; i < numsArr.length; i++) {
        const num = parseInt(numsArr[i], 10);
        if (!isNaN(num)) {
            result.push(strs.substring(strIndex, strIndex + num));
            strIndex += num;
        }
    }

    return result;
};

module.exports = { encode, decode, DELIMITER };