LeetCode 720. 詞典中最長的單詞 (字典樹的簡單應用)

詞典中最長的單詞
① 首先把n的字符串插入字典樹
② 然後依次查詢n的字符串是否滿足要求——它的每個字符都是某個字符串的結尾。

class Solution {
    string ans = "";
    struct Node{   
        bool isEnd = false;
        Node* children[26] = {0};
    };
    Node* root = new Node;

    void insert(const string &s){
        Node* p = root;
        for(char c:s){
            if(!p->children[c-'a']){
                p->children[c-'a'] = new Node;
            }
            p = p->children[c-'a'];
        }
        p->isEnd = true;
    }

    bool find(const string &s){
        Node* p = root;
        for(char c:s){
            if(!p->children[c-'a']  || !p->children[c-'a']->isEnd){
                return false;
            }
            p = p->children[c-'a'];
        }
        return true;
    }

public:
    string longestWord(vector<string>& words) {
        for(string &s:words){
            insert(s);
        }
        for(string &s:words){
            if(find(s)){

                if(s.size()>ans.size()){
                    ans = s;
                }else if(s.size()==ans.size()){
                    ans = min(ans,s);
                }
            }
        }
        return ans;
    }
};