LeetCode OJ：Add and Search Word

Design a data structure that supports the following two operations:

void addWord(word)
bool search(word)

search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.

For example:

addWord("bad")
addWord("dad")
addWord("mad")
search("pad") -> false
search("bad") -> true
search(".ad") -> true
search("b..") -> true

这题用set做的话可能会超时，应该自己定义数据结构，构造一个单词数，这样效率更高，在搜索的时候就是dfs了， 代码如下：

class WordDictionary {
public:
    struct TreeNode{
    public:
        TreeNode *child[26];
        bool isWord;

        TreeNode() : isWord(false){
            for(auto & a : child)
                a = NULL;
        }
    };

    WordDictionary() {
        root = new TreeNode();
    }

    // Adds a word into the data structure.
    void addWord(string word) {
        TreeNode * p = root;
        for(auto & a : word){
            if(!p->child[a-'a'])
                p->child[a-'a'] = new TreeNode;
            p = p->child[a-'a'];
        }
        p->isWord = true;//标记一个单词
    }


    bool searchWord(string & word, TreeNode * p, int index)
    {
        if(word.size() == index) return p->isWord;//这条很关键
        if(word[index] == '.'){
            for(auto & a : p->child){
                if(a && searchWord(word, a, index+1)) return true;
            }
            return false;//不要忘了
        }else{
            return (p->child[word[index] - 'a'])&&searchWord(word, p->child[word[index] - 'a'], index+1);
        }
    }


    bool search(string word) {
        return searchWord(word, root, 0);
    }




    // WordDictionary()//进入函数后会首先执行构造函数
    // : root(new TreeNode) {}
private:
    TreeNode * root;
};

这回写的比较乱，见谅