circularstation.cpp

#include <algorithm>
#include <iostream>
#include <random>

struct Task {
    static const int STATION_SIZE = 50;

    std::vector<bool> lights;
    int room;

    Task() {
        std::mt19937 generator((std::random_device()()));
        lights.resize(size_t(STATION_SIZE));
        for (int i = 0; i < STATION_SIZE; ++i) {
            lights[i] = std::uniform_int_distribution<>(0, 1)(generator) != 0;
        }

        room = 0;
    }

    void next() {
        room = room < STATION_SIZE - 1 ? room + 1 : 0;
        dump();
    }

    void previous() {
        room = room > 0 ? room - 1 : STATION_SIZE - 1;
        dump();
    }

    void dump() {
        printf("\r"); for(int i=0; i<STATION_SIZE; i++) printf("%d",lights[i]?1:0);
        //printf("\r"); for(int i=0; i<room; i++) printf(" "); printf("^\n");
        //system("pause");
    }

    bool isLightEnabled() {
        return lights[room];
    }

    void toggleLight() {
        lights[room] = !lights[room];
        dump();
    }

    void explore() {
        // DO NOT MODIFY FILE ABOVE THIS LINE
        // You should leave this function when you have disabled lights in all the station rooms
        // Use only 'next()', 'previous()', 'isLightEnabled()', 'toggleLight()', 'break', 'continue', 'do', 'else', 'for', 'if', 'return' and 'while'
        // No constants, defines, includes, lambdas, variables, templates, no other function calls except 4 functions above
        // No more than 1 KB of code
        // Solution should be resistant to source data changes, including 'STATION_SIZE', initial state of 'lights' vector and 'room' variable


        // check for special case (STATION_SIZE==1)
        if (!isLightEnabled()) toggleLight(); next(); toggleLight(); previous(); if (!isLightEnabled()) return;
        // light up 2 markers
        if (!isLightEnabled()) toggleLight(); next();
        if (!isLightEnabled()) toggleLight(); next();
        // pingpong
        for (;;) {
            while (!isLightEnabled()) next();
            toggleLight();
            while (!isLightEnabled()) previous();
            previous();
            if (!isLightEnabled()) break;
            next();
            next();
        }
        // cleanup
        next();
        toggleLight();

        // DO NOT MODIFY FILE BELOW THIS LINE
    }

    bool validate() {
        return std::find(lights.begin(), lights.end(), true) == lights.end();
    }
};

int main() {
    Task t;

    t.explore();

    if (t.validate()) {
        std::cout << "success\n";
    } else {
        std::cout << "failure\n";
    }
}