EncodeandDecodeStrings.java

package leetcode;

import java.util.ArrayList;
import java.util.List;

/**
 * Project Name : Leetcode
 * Package Name : leetcode
 * File Name : EncodeandDecodeStrings
 * Creator : Edward
 * Date : Oct, 2017
 * Description : 271. Encode and Decode Strings
 */
public class EncodeandDecodeStrings {


    /**
     * time : O(n);
     * space : O(n)
     * @param strs
     * @return
     */

    // Encodes a list of strings to a single string.
    public String encode(List<String> strs) {
        StringBuilder sb = new StringBuilder();
        for (String str : strs) {
            sb.append(str.length()).append('/').append(str);
        }
        return sb.toString();
    }

    // Decodes a single string to a list of strings.
    public List<String> decode(String s) {
        List<String> res = new ArrayList<>();
        int i = 0;
        while (i < s.length()) {
            int slash = s.indexOf('/', i);
            int size = Integer.valueOf(s.substring(i, slash));
            res.add(s.substring(slash + 1, slash + size + 1));
            i = slash + size + 1;
        }
        return res;
    }
}