Here are two versions in plain ANSI C++.

#include <string>
#include <sstream>
#include <iostream>

using namespace std;

static string reverseWords(string const& instr)
{
    istringstream iss(instr);
    string outstr;
    string word;
    iss >> outstr;
    while (iss >> word)
        outstr = word + ' ' + outstr;
    return outstr;
}

int main()
{
    string s = "   one   two \t three four  ";
    string sret = reverseWords(s);
    cout << "in='" << s << "' " << "out='" << sret << "'" << endl;
    return 0;
}
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#include <string>
#include <sstream>
#include <iostream>
#include <deque>
#include <algorithm>

using namespace std;

static string reverseWords(string const& instr)
{
    istringstream iss(instr);
    deque<string> dqs;
    copy(istream_iterator<string>(iss), istream_iterator<string>(),
        front_inserter(dqs));
    if (dqs.empty()) return "";

    ostringstream oss;
    copy(dqs.begin(), --dqs.end(), ostream_iterator<string>(oss, " "))
+;
    oss << dqs.back();
    return oss.str();
    // ... or build string directly instead of using ostringstream
    // string outstr(dqs.front());
    // for (deque<string>::const_iterator i = ++dqs.begin(); i != dqs.
+end(); ++i)
    //     outstr += ' ' + *i;
    // return outstr;
}

int main()
{
    string s = "   one   two \t three four  ";
    string sret = reverseWords(s);
    cout << "in='" << s << "' " << "out='" << sret << "'" << endl;
    return 0;
}
[download]