676. Implement Magic Dictionary

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LeetCode

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Problem

Design a data structure that is initialized with a list of different words. Provided a string, you should determine if you can change exactly one character in this string to match any word in the data structure.

Implement the MagicDictionary class:

• MagicDictionary() Initializes the object.
• void buildDict(String[] dictionary) Sets the data structure with an array of distinct strings dictionary.
• bool search(String searchWord) Returns true if you can change exactly one character in searchWord to match any string in the data structure, otherwise returns false.

Example 1:

Input
["MagicDictionary", "buildDict", "search", "search", "search", "search"]
[[], [["hello", "leetcode"]], ["hello"], ["hhllo"], ["hell"], ["leetcoded"]]
Output
[null, null, false, true, false, false]

Explanation
MagicDictionary magicDictionary = new MagicDictionary();
magicDictionary.buildDict(["hello", "leetcode"]);
magicDictionary.search("hello"); // return False
magicDictionary.search("hhllo"); // We can change the second 'h' to 'e' to match "hello" so we return True
magicDictionary.search("hell"); // return False
magicDictionary.search("leetcoded"); // return False

Constraints:

• 1 <= dictionary.length <= 100
• 1 <= dictionary[i].length <= 100
• dictionary[i] consists of only lower-case English letters.
• All the strings in dictionary are distinct.
• 1 <= searchWord.length <= 100
• searchWord consists of only lower-case English letters.
• buildDict will be called only once before search.
• At most 100 calls will be made to search.

Code

class MagicDictionary {
    class Node {
        char c;
        int index;

        Node(char c, int index){
            this.c = c;
            this.index = index;
        }
    }

    Map<String, List<Node>> map;
    public MagicDictionary() {
        map = new HashMap<>();
    }

    public void buildDict(String[] dict) {
        for (String word : dict) {
            for (int i = 0; i < word.length(); i++) {
                String key = word.substring(0, i) + word.substring(i + 1);
                Node node = new Node(word.charAt(i), i);

                if(!map.containsKey(key)){
                    map.put(key, new ArrayList<>());
                }

                map.get(key).add(node);
            }
        }
    }

    public boolean search(String word) {
        for (int i = 0; i < word.length(); i++) {
            String key = word.substring(0, i) + word.substring(i + 1);

            if (map.containsKey(key)) {
                for (Node node : map.get(key)) {
                    if (node.index == i && node.c != word.charAt(i)) return true;
                }
            }
        }

        return false;
    }
}