44. 翻转单词顺序列

题目描述：牛客最近来了一个新员工Fish，每天早晨总是会拿着一本英文杂志，写些句子在本子上。同事Cat对Fish写的内容颇感兴趣，有一天他向Fish借来翻看，但却读不懂它的意思。例如，“student. a am I”。后来才意识到，这家伙原来把句子单词的顺序翻转了，正确的句子应该是“I am a student.”。Cat对一一的翻转这些单词顺序可不在行，你能帮助他么？

思路：题目要求把类似于 "student. a am I"翻转为"I am a student."

直接看程序吧！

class Solution {
public:
    string ReverseSentence(string str) {
        int len = str.size();
        if(len <= 0)
            return "";
        string str1 = "";
        string temp = "";
        for(int i = len - 1; i >= 0; -- i)
        {
            if(i == 0)
            {
                temp += str[i];
                str1 += ReverseStr(temp);
            }
            else if(str[i] == ' ')
            {
                str1 += ReverseStr(temp);
                str1 += str[i];
                temp = "";
            }
            else
                temp += str[i];
        }
        return str1;
    }
    string ReverseStr(string str)
    {
        int len = str.size();
        if(len == 0)
            return "";
        string temp = "";
        for(int i = len - 1; i >= 0; -- i)
        {
            temp += str[i];
        }
        return temp;
    }
};

class Solution {
public:
    string ReverseSentence(string str) {
        string res = "", tmp = "";
        for(int i = 0; i < str.size(); ++i){
            if(str[i] == ' ') 
            {
                res = " " + tmp + res;
                tmp = "";
            }
            else 
                tmp += str[i];
        }
        if(tmp.size()) 
            res = tmp + res;
        return res;
    }
};