659.encode-and-decode-strings.cpp

//  Tag: String
//  Time: O(N)
//  Space: O(1)
//  Ref: Leetcode-271
//  Note: -

//  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`
//  
//  **Example1**
//  ```
//  Input: ["lint","code","love","you"]
//  Output: ["lint","code","love","you"]
//  Explanation:
//  One possible encode method is: "lint:;code:;love:;you"
//  ```
//  **Example2**
//  ```
//  Input: ["we", "say", ":", "yes"]
//  Output: ["we", "say", ":", "yes"]
//  Explanation:
//  One possible encode method is: "we:;say:;:::;yes"
//  ```
//  
//  Because the string may contain any of the **256** legal ASCII characters, your algorithm must be able to handle any character that may appear
//  
//  Do not rely on any libraries, the purpose of this problem is to implement the "encode" and "decode" algorithms on your own

class Solution {
public:
    /*
     * @param strs: a list of strings
     * @return: encodes a list of strings to a single string.
     */
    string encode(vector<string> &strs) {
        // write your code here
        string res;
        for (string &str: strs) {
            for (char c: str) {
                if (c == ':') {
                    res += "::";
                } else {
                    res += c;
                }
            }
            res += ":;";
        }
        return res;
    }

    /*
     * @param str: A string
     * @return: decodes a single string to a list of strings
     */
    vector<string> decode(string &str) {
        // write your code here
        vector<string> res;
        string word;
        int i = 0;
        while (i < str.size()) {
            if (str[i] == ':') {
                if (str[i + 1] == ':') {
                    word += ':';
                } else {
                    res.push_back(word);
                    word = "";
                }
                i += 2;
            } else {
                word += str[i];
                i += 1;
            }


        }
        return res;
    }
};