271. Encode and Decode Strings [Medium]

271. Encode and Decode Strings

居然要premium才能做，果断换LintCode来写这题
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

Example

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

思路

只要知道每一个String长度，然后记录他的长度，那解码的时候就可以依据他的长度，拿到该String，关键在于只存长度还是有点问题，因为如果String中也有数字，那就不知道在哪边截断，取出正确的字符串长度，所以可以自定义一个字符。
规则应该是String.length + Special Char + String

题解

• 无脑快速AC

/*
     * @param strs: a list of strings
     * @return: encodes a list of strings to a single string.
     */
    public String encode(List<String> strs) {
        // write your code here
        String res = "";
        for (String val : strs) {
            res += (val.length() + "," + val);
        }
        return res;
    }

    /*
     * @param str: A string
     * @return: dcodes a single string to a list of strings
     */
    public List<String> decode(String str) {
        // write your code here
        ArrayList<String> result = new ArrayList<>();
        while (!str.equals("")) {
	    // 拿到截断字符串的下标，
            int splitIndex = str.indexOf(",");
	    // 通过该下标，直接截断字符串取出当前待解码字符串长度
            Integer strLength = Integer.valueOf(str.substring(0, splitIndex));
	    // 设置待解码字符串在当前编码字符串中的起始位置
            int start = splitIndex + 1;
	    // 算出结束位
            int end = start + strLength;
            String curStr = str.substring(start, end);
            result.add(curStr);
	    //  直接将当前已插入结果集的子串截去，substring不太熟练，+1-1搞晕
            str = str.substring(end);
        }
        return result;
    }