https://leetcode.com/problems/add-and-search-word-data-structure-design/

本题是在Trie树进行dfs+backtracking操作。

Trie树模板代码见:http://www.cnblogs.com/fu11211129/p/4952255.html

题目介绍:

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

Note:
You may assume that all words are consist of lowercase letters a-z.

struct Trie{
Trie *next[]; //include character '.'
bool isWord;
Trie() {
for(auto &n : this->next) n = NULL;
this->isWord = false;
}
};
class WordDictionary {
public:
Trie *root;
WordDictionary() {
this->root = new Trie();
} void insert(string s) {
Trie *p = this->root;
for(auto &c: s) {
int idx = c - 'a';
if(!p->next[idx]) p->next[idx] = new Trie();
p = p->next[idx];
}
p->isWord = true;
} void addWord(string word) {
insert(word);
} bool dfs(Trie *p, string word, int idx) {
if(idx == word.size()-) {
if(word[idx] == '.') {
for(int i=;i<;++i) {
if(p->next[i] != NULL && p->next[i]->isWord) return true;
}
return false;
}
else {
int nidx = word[idx] - 'a';
if(p->next[nidx] == NULL) return false;
else return p->next[nidx]->isWord;
}
} if(word[idx] == '.') {
for(int i=;i<;++i) {
if(p->next[i] != NULL && dfs(p->next[i], word, idx+)) return true;
}
}
else {
int nidx = word[idx] - 'a';
if(! p->next[nidx]) return false;
if(p->next[nidx] && dfs(p->next[nidx], word, idx+)) return true;
}
return false;
} // Returns if the word is in the data structure. A word could
// contain the dot character '.' to represent any one letter.
bool search(string word) {
bool flag = false;
for(int i=;i<;++i) {
if(root->next[i] != NULL) {
flag = true; break;
}
}
if(!flag) return false; return dfs(root, word, );
}
}; // Your WordDictionary object will be instantiated and called as such:
// WordDictionary wordDictionary;
// wordDictionary.addWord("word");
// wordDictionary.search("pattern");

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