【Leetcode_easy】720. Longest Word in Dictionary

problem

720. Longest Word in Dictionary

题意：

solution1: BFS;

class Solution {
public:
    string longestWord(vector<string>& words) {
        string res = "";
        unordered_set<string> s(words.begin(), words.end());
        queue<string> q;
        for(auto word:words)
        {
            if(word.size()==1) q.push(word);
        }
        int maxLen = 0;
        while(!q.empty())
        {
            string t = q.front();
            q.pop();
            if(t.size()>maxLen) 
            {
                maxLen = t.size();
                res = t;//err....
            }
            else if(t.size()==maxLen) res = min(res, t);
            for(char ch='a'; ch<='z'; ++ch)//err...
            {
                t.push_back(ch);
                if(s.count(t)) q.push(t);
                t.pop_back();
            }
        }
        return res;
    }
};

solution2:

class Solution {
public:
    string longestWord(vector<string>& words) {
        string res = "";
        unordered_set<string> s(words.begin(), words.end());
        int maxLen = 0;
        for (auto word:words)
        {
            if(word.size()==1) helper(s, word, maxLen, res);
        }
        return res;
    }
    void helper(unordered_set<string>& s, string word, int& maxLen, string& res) {
        if(word.size()>maxLen)
        {
            maxLen = word.size();
            res = word;
        }
        else if(word.size()==maxLen) res = min(res, word);
        for(char ch = 'a'; ch<='z'; ++ch)
        {
            word.push_back(ch);
            if(s.count(word)) helper(s, word, maxLen, res);
            word.pop_back();
        }
    }
};

 

参考

1. Leetcode_easy_720. Longest Word in Dictionary;

2. Grandyang;

完