820. 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.

Solution:
HashSet method:

• build set to store words array
• iterate all words and remove all suffixes of every word from set to get final set
• iterate final set to sum every word length plus 1 as for “#”

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class Solution {
    public int minimumLengthEncoding(String[] words) {
        Set<String> s= new HashSet<>(Arrays.asList(words));
        for (String word: words) {
            for(int i=1; i<words.length; i++) {
                s.remove(word.substring(i));
            }
        }
        int res = 0;
        for (String w: s) {
            res += w.length() + 1;
        }
        return res;
    }
}

references

• https://leetcode.com/problems/short-encoding-of-words/