剑指offer---翻转单词顺序

class Solution
{
public:
    void fanzhuandanci(string &word, int start, int end)
    {
        int i = start;
        int j = end;
        while (i <= j)
        {
            swap(word[i], word[j]);
            ++i;
            --j;
        }
    }
    string ReverseSentence(string str)
    {
        str +=" ";
        fanzhuandanci(str,0,str.size()-1);
        str +=" ";
        

        int start = 0;
        int end = 0;
        while (start<str.size())
        {
            while (str[start] == ‘ ‘&&start<str.size())
            {
                ++start;
            }

            end = start;
            while (str[end] != ‘ ‘&&end<str.size())
            {
                ++end;
            }
            --end;

            fanzhuandanci(str, start, end);
            ++end;
            start = end;
        }

        return str.substr(1,str.size()-2);
    }
};