PrQueue

#include <queue>
#include <fstream>
#include <iostream>
#include <cstdio>
#include <cctype>
#include <string>
#define IS_DELIM (c == ' ' || c == '\t' ||  c == '\n')

using namespace std;

int main(void) {
    ifstream in ("input.txt");
    ofstream out ("output.txt");
    queue<string> small;
    queue<string> big;
    queue<char> current;

    char c;
    while (in >> noskipws >> c)
    {
        current.push(c);
    }

    bool begin = true;
    string s;
    while (current.size())
    {
        c = current.front();
        current.pop();
        if (!IS_DELIM)
        {
            begin = false;
            s += c;
        }
        else if (s.size())
        {
                if (islower(s[0])) small.push(s);
                else big.push(s);
                s.clear();
                begin = true;
        }
    }

    while (small.size())
    {
        out << small.front() << " ";
        small.pop();
    }

    while (big.size())
    {
        out << big.front() << " ";
        big.pop();
    }
}