211. Design Add and Search Words Data Structure

Design a data structure that supports adding new words and finding if a string matches any previously added string.

Implement the WordDictionary class:

  • WordDictionary() Initializes the object.
  • void addWord(word) Adds word to the data structure, it can be matched later.
  • bool search(word) Returns true if there is any string in the data structure that matches word or false otherwise. word may contain dots '.' where dots can be matched with any letter.

 

Example:

Input
["WordDictionary","addWord","addWord","addWord","search","search","search","search"]
[[],["bad"],["dad"],["mad"],["pad"],["bad"],[".ad"],["b.."]]
Output
[null,null,null,null,false,true,true,true]

Explanation
WordDictionary wordDictionary = new WordDictionary();
wordDictionary.addWord("bad");
wordDictionary.addWord("dad");
wordDictionary.addWord("mad");
wordDictionary.search("pad"); // return False
wordDictionary.search("bad"); // return True
wordDictionary.search(".ad"); // return True
wordDictionary.search("b.."); // return True

 

Constraints:

  • 1 <= word.length <= 500
  • word in addWord consists lower-case English letters.
  • word in search consist of  '.' or lower-case English letters.
  • At most 50000 calls will be made to addWord and search.

Rust Solution

use std::collections::HashMap;

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

impl Trie {
    fn insert(&mut self, s: &str) {
        let mut link = self;
        for c in s.chars() {
            link = link.children.entry(c).or_default();
        }
        link.end = true;
    }

    fn search(&self, s: &str) -> bool {
        if s.is_empty() {
            return self.end;
        }
        let c = s.chars().next().unwrap();
        if c == '.' {
            for child in self.children.values() {
                if Self::search(child, &s[1..]) {
                    return true;
                }
            }
        } else {
            if let Some(child) = self.children.get(&c) {
                return Self::search(&child, &s[1..]);
            } else {
                return false;
            }
        }
        false
    }
}

#[derive(Default)]
struct WordDictionary {
    trie: Trie,
}

impl WordDictionary {
    fn new() -> Self {
        WordDictionary {
            trie: Trie::default(),
        }
    }
    fn add_word(&mut self, word: String) {
        self.trie.insert(&word);
    }
    fn search(&self, word: String) -> bool {
        self.trie.search(&word)
    }
}

#[test]
fn test() {
    let mut wd = WordDictionary::new();
    wd.add_word("bad".to_string());
    wd.add_word("dad".to_string());
    wd.add_word("mad".to_string());
    assert_eq!(wd.search("pad".to_string()), false);
    assert_eq!(wd.search("bad".to_string()), true);
    assert_eq!(wd.search(".ad".to_string()), true);
    assert_eq!(wd.search("b..".to_string()), true);
}

Having problems with this solution? Click here to submit an issue on github.