Today I have done leetcode's March LeetCoding Challenge with cpp.

March LeetCoding Challenge 19

Description

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 <= 25
• word in addWord consists of lowercase English letters.
• word in search consist of '.' or lowercase English letters.
• There will be at most 3 dots in word for search queries.
• At most 104 calls will be made to addWord and search.

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
struct TrieNode {
  bool end = false;
  TrieNode *children[26] = {};
};

class WordDictionary {
  TrieNode *root;

  bool helper(const string &word, TrieNode *cur, int pos = 0) {
    int len = word.length();
    for(int i = pos; i < len; ++i) {
      if(word[i] != '.') {
        if(!cur->children[word[i] - 'a']) return false;
        cur = cur->children[word[i] - 'a'];
      } else {
        for(auto child : cur->children) {
          if(child && helper(word, child, i + 1)) return true;
        }
        return false;
      }
    }
    return cur->end;
  }
public:
  WordDictionary() {
    root = new TrieNode();
  }
  
  void addWord(string word) {
    TrieNode *cur = root;
    for(auto c : word) {
      c -= 'a';
      if(!cur->children[c]) {
        cur->children[c] = new TrieNode();
      }
      cur = cur->children[c];
    }
    cur->end = true;
  }
  
  bool search(string word) {
    return helper(word, root);
  }
};

// Accepted
// 29/29 cases passed (859 ms)
// Your runtime beats 94.41 % of cpp submissions
// Your memory usage beats 72.66 % of cpp submissions (558.4 MB)