leetcode - Reverse Words in a String

class Solution {
public:
    void reverseWords(string &s) {
        reverse(s.begin(), s.end()); //reverse the whole string.
        string::iterator it = s.begin();
        while(it!=s.end()){
            while(it != s.end() && *it==‘ ‘){
                if(*(it+1)==‘ ‘){ it = s.erase(it);}
               //if the next one is space, erase the current one.
               // erase will return the next iterator.
                else{it++;} // else it++
            }
            string::iterator beg = it;
            while(it != s.end() && *it!=‘ ‘){
                it++;
            }
            string::iterator end = it;
            reverse(beg,end); // reverse each words.
        }
        if(*(s.begin()) == ‘ ‘) s.erase(s.begin()); // remove the first space
        if(*(s.end()-1) == ‘ ‘) s.erase(s.end()-1); // remove the last space.
    }
};