https://www.codeeval.com/open_challenge_scores/?pkbid=5

cycle_detection.cpp

#include <iostream>
#include <sstream>
#include <fstream>
#include <vector>
#include <set>
#include <iterator>

#ifndef __APPLE__
#include <algorithm>
#endif

using namespace std;

struct Number {
    size_t index;
    int value;

    Number(const int value, const size_t index) {
        this->value = value;
        this->index = index;
    }

    Number(const int value) {
        this->value = value;
        this->index = -1;
    }

    bool operator== (const Number& other) const {
        return (other.value == this->value);
    }

    bool operator< (const Number& other) const {
        return (other.value < this->value);
    }
};

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

    ifstream datafile(argv[1]);
    string line;

    while (getline(datafile, line)) {

        if (line.length() < 1) {
            cout << endl;
            continue;
        }

        vector<int> numbers;
        set<Number> check;

        istringstream stream(line);
        string token;

        while (getline(stream, token, ' ')) {
            istringstream converter(token);
            int number;
            converter >> number;
            numbers.push_back(number);
        };

        ostringstream out;

        size_t loop_length = 0;

        for (vector<int>::iterator it = numbers.begin(); it < numbers.end(); ++it) {
            int number = *it;
            Number candidate = Number(number);
            set<Number>::iterator existing = check.find(candidate);
            if (existing != check.end()) {
                for (size_t x = (*existing).index; x < loop_length; ++x) {
                    out << numbers.at(x) << " ";
                }
                break;
            }
            check.insert(Number(number, loop_length));
            loop_length++;
        }

        out << " ";

        string result = out.str();
        result.resize(result.length() - 2);
        cout << result << endl;
    }

    return 0;
}

data.txt

1 2 3 4 5 6 7 8 9 11 11 11 11
1 2 3 4 5 6 7 8 9 11 11 11 11 4 5 6
99 98 97 96 95 94 93 92 91 95 94 93 92 91 90
4 57 57 57 57 57 57 57 57 57 57 57 57 57 57
2 0 6 3 1 6 3 1 6 3 1
3 4 8 0 11 9 7 2 5 6 10 1 49 49 49 49
1 2 3 1 2 3 1 2 3