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.

Rust Solution

struct Solution;

use std::collections::HashMap;

#[derive(PartialEq, Eq, Default)]
struct Trie {
    children: HashMap<char, Trie>,
    end: bool,
}

impl Trie {
    fn new() -> Self {
        Self::default()
    }
    fn insert<I>(&mut self, iter: I)
    where
        I: Iterator<Item = char>,
    {
        let mut link = self;
        for c in iter {
            link = link.children.entry(c).or_default();
        }
        link.end = true;
    }

    fn dfs(&self, length: usize, sum: &mut usize) {
        let mut is_leaf = true;
        for link in self.children.values() {
            is_leaf = false;
            link.dfs(length + 1, sum);
        }
        if is_leaf {
            *sum += length + 1;
        }
    }
}

impl Solution {
    fn minimum_length_encoding(words: Vec<String>) -> i32 {
        let mut trie = Trie::new();
        for word in words {
            trie.insert(word.chars().rev());
        }
        let mut res = 0;
        trie.dfs(0, &mut res);
        res as i32
    }
}

#[test]
fn test() {
    let words = vec_string!["time", "me", "bell"];
    let res = 10;
    assert_eq!(Solution::minimum_length_encoding(words), res);
}

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