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 root forming 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:The input will only have lower-case letters.1 <= dict words number <= 10001 <= sentence words number <= 10001 <= root length <= 1001 <= sentence words length <= 1000思路：  把dict中的内容添加到set中，便于查找  把sentence根据“ ”分成若干个单词  对每个单词中的前缀在set中进行查找，如果找到则进行修改  重组句子*/class Solution {public:    string replaceWords(vector<string>& dict, string sentence) {        set<string> myDict;        for(int i=0;i<dict.size();i++)            myDict.insert(dict[i]);        vector<string> mySentence;        for(int i=0,j=0;i<sentence.size() && j<=sentence.size();j++)//把字符串分成单词        {            if(sentence[j]==' ' || j==sentence.size())            {                mySentence.push_back(sentence.substr(i,j-i));                i=j+1;            }        }        string res="";        for(int i=0;i<mySentence.size();i++)        {                       for(int j=0;j<mySentence[i].size();j++)            {                if(myDict.find(mySentence[i].substr(0,j+1)) != myDict.end())                {                    mySentence[i]=mySentence[i].substr(0,j+1);                    break;                }            }            res+=(mySentence[i]+" ");        }        return res.substr(0,res.size()-1);    }};