main.cpp

#include <cstdlib>
#include <iostream>
#include <unordered_map>
#include <vector>
#include <iomanip>
#include <algorithm>
#include <unistd.h>

using namespace std;

string to_lower(const string& str) {

    string ret;

    transform(str.begin(), str.end(), back_inserter(ret), ::tolower);

    return ret;
}

int main(int argc, char *argv[]) {

	int c, s=0, w=-1;
	bool ignore_case= false;
    while ((c = getopt(argc, argv, "is:w:")) != -1) {
		switch (c) {
			case 'i':
				ignore_case=true;
				break;
            case 's':
                s = atoi(optarg);
                break;
            case 'w':
                w = atoi(optarg);
                break;
			default:
				abort(); // fix this later...
		}
	}

    unordered_map<string, int> htable;
    string line;

    vector<string> keys;
    keys.reserve(htable.size());

    while (cin >> line) {


        // FIXME: Don't like this way, we'd be better off updating the
        //        key_equal & hasher...
        if ( w != -1 )  
            line = line.substr(s,w);
        else if ( s > 0)
            line = line.substr(s, string::npos);

		if (ignore_case) // FIXME: This will do for now, but ideally we should
						 //        just update the key_equal & hasher 
			line = to_lower(line); 
       if ( htable.find(line) == htable.end() ) // if not in htable already:
           keys.push_back(line); // add to keys vector
       htable[line]++;
    }

    // this ultimately should be optional
    sort(keys.begin(), keys.end()); //sort our keys vector

    for (auto& it : keys) //iterate through keys, printing from htable
        cout << setfill(' ') << setw(7) << htable[it] << " " << it << endl;

    exit(EXIT_SUCCESS);

}