Reverse Words in a String.cpp

// Runtime: 23 ms (Top 19.68%) | Memory: 20.6 MB (Top 34.65%)
class Solution {
public:
    string reverseWords(string s) {
        int i=0;
        string res = "";
        while(i<s.length())
        {
            while(i<s.length() && s[i]==' ')
                i++;

            if(i>=s.length())
                break;

            int j=i+1;

            while(j<s.length() && s[j]!=' ')
                j++;

            string tmp = s.substr(i,j-i);
            if(res.length()==0)
            {
                res = tmp;
            }
            else
            {
                res = tmp + " " + res;
            }
            i=j+1;
        }
        return res;
    }
};