LeetCode - Short Encoding of Words

A valid encoding of an array of words is any reference string s and array of indices indices such that:

words.length == indices.length
The reference string s ends with the '#' character.
For each index indices[i], the substring of s starting from indices[i] and up to (but not including) the next '#' character is equal to words[i].
Given an array of words, return the length of the shortest reference string s possible of any valid encoding of words.

 

Example 1:

Input: words = ["time", "me", "bell"]
Output: 10
Explanation: A valid encoding would be s = "time#bell#" and indices = [0, 2, 5].
words[0] = "time", the substring of s starting from indices[0] = 0 to the next '#' is underlined in "time#bell#"
words[1] = "me", the substring of s starting from indices[1] = 2 to the next '#' is underlined in "time#bell#"
words[2] = "bell", the substring of s starting from indices[2] = 5 to the next '#' is underlined in "time#bell#"
Example 2:

Input: words = ["t"]
Output: 2
Explanation: A valid encoding would be s = "t#" and indices = [0].

 

Constraints:

1 <= words.length <= 2000
1 <= words[i].length <= 7
words[i] consists of only lowercase letters.

 

class Solution {
    public int minimumLengthEncoding(String[] words) {
        Arrays.sort(words, (s1, s2) -> {
            return s2.length()-s1.length();
        });
        StringBuilder sb = new StringBuilder();
        for (String word : words) {
            String curStr = sb.toString();
            int foundIndex = curStr.lastIndexOf(word);
            if(foundIndex != -1 && curStr.charAt(foundIndex+word.length()) == '#') {
                continue;
            }
            sb.append(word + "#");
        }
        return sb.length();
    }
}