Reverse Words in a String II

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.

The input string does not contain leading or trailing spaces and the words are always separated by a single space.

For example,

Given s = "the sky is blue",

return "blue is sky the".

Could you do it in-place without allocating extra space? 

#include<iostream>
#include<string>
#include<algorithm>
using namespace std;

string reverword(string);
void reversestr(string&, int, int);
int main()
{
string data[] = { "the sky is blue"};

for (string s : data)
{
reversestr(s, 0, s.size() - 1);
cout << s << endl;

}
for (string s : data)
{
cout << reverword(s) << endl;

}
system("pause");
return 0;
}

string reverword(string str)
{
int len = str.size() - 1;
reversestr(str, 0, len);
cout << str << endl;
string temp;

//下面分割字符串
int i = 0;
int j=0;
// i记录到‘’的位置
//j 记载非‘ ’的位置

while (i < len + 1)
{
if (str[i] != ' ')
{
i++;
if (i == len)
{
reversestr(str, j, i);
}
}
else
{
reversestr(str,j, i-1);
j = i + 1;
i++;

}
}
return str;
}

void reversestr(string& strr, int a, int b)
{

int left = a;
int right = b;
while (left < right)
{
char temp = strr[left];
strr[left] = strr[right];
strr[right] = temp;
left++;
right--;
}
}