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

January LeetCoding Challenge 28

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 <= 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.

Solution

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

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();
  }

  ~WordDictionary() {
    delete root;
  }
  
  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
// 13/13 cases passed (84 ms)
// Your runtime beats 75.72 % of cpp submissions
// Your memory usage beats 57.03 % of cpp submissions (43.7 MB)