// 翻轉單詞順序序列
    // 先翻轉所有單詞，再逐個單詞翻轉


    string ReverseSentence(string str) {
        if (str.size() == 0) {
            return " ";
        }
        Reverse(str, 0, str.size() - 1); //翻轉所有單詞
        int left = 0, right = 0;
        while (right <= str.size()) {//逐個單詞翻轉
            if ((str[right] == ' ') || (right == str.size() && str.size() -1) != ' ') {
                /*for (int i = 0; i < right; i++) { // 遇見空格和字串最後一個位置
                    cout << str[i] << ' ';
                }*/

                Reverse(str, left, right - 1);
                left = right + 1;
            }
            right++;


        }

        return str;
    }


    

    void Reverse(string &str, int left, int right) {
        while (left < right) {
            char temp = str[left];
            str[left] = str[right];
            str[right] = temp;
            //swap (str[left], str[right]);
            left++;
            right--;
        }
    }