648. Replace Words

In English, we have a concept called root, which can be followed by some other words to form another longer word - let‘s call this word successor. For example, the root an, followed by other, which can form another word another.

Now, given a dictionary consisting of many roots and a sentence. You need to replace all the successor in the sentence with the rootforming it. If a successor has many roots can form it, replace it with the root with the shortest length.

You need to output the sentence after the replacement.

Example 1:

Input: dict = ["cat", "bat", "rat"]
sentence = "the cattle was rattled by the battery"
Output: "the cat was rat by the bat"

Note:

1. The input will only have lower-case letters.
2. 1 <= dict words number <= 1000 
3. 1 <= sentence words number <= 1000 
4. 1 <= root length <= 100 
5. 1 <= sentence words length <= 1000

class Solution {
public:
    string replaceWords(vector<string>& dict, string sentence) {
        string res;
        unordered_map<string,bool>mp;
        for(auto word:dict)mp[word]=true;
        istringstream is(sentence);
        string token;
        while(is>>token)
        {
            int i = 1;
            int n = token.size();
            for(i = 1;i<=n;i++)
            {
                string s = token.substr(0,i);
                if(mp.find(s)!=mp.end())
                {
                    res += s+" ";
                    break;
                }
            }
            if(i==n+1)
                res+=token+" ";
        }
        return res.substr(0,res.size()-1);
    }
};