Simple C++ Puzzle Game

// THIS IS ONLY A MIRROR POST
// ORIGINAL: https://zekro.de/gist/puzzle

/*
    Simple Puzzle Game v.1.5
    © 2018 Ringo Hoffmann

    IDEAS:
    ✔ debug start argument
    - entering seed before start
    ✔ saving high score
    - better randomizer
    - exclude unsolvable cases of
      start field
    - customizable size
*/

#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
#include <math.h>

using namespace std;


const char *VERSION = "1.5";
const char *HS_FILENAME = "highscore.dat";

// moves counter
int moves = 0, highscore, debug_mode = 0;

// Initializing 2-dimensional field
int f[3][3];

// clear display help function
void cls() {
#ifdef _WIN32 || _WIN64
    system("cls");
#else
    system("clear");
#endif
}

// printing field with moves count
void print_field() {
    cls();
    if (debug_mode)
        cout << "DEBUG MODE ENABLED\n\n";
    cout << "Puzzle Game by Ringo Hoffmann\n© 2018\n"
        << "v." << VERSION << "\n\n"
        << "[Start with argument '-r' to reset highscore.]\n\n"
        << "Move:      " << moves + 1 << "\n"
        << "Highscore: ";
    if (highscore == -1)
        cout << "not set yet\n\n";
    else
        cout << highscore << "\n\n";

    cout << " +-------+\n";
    for (int i = 0; i < 3; i++) {
        cout << " | ";
        for (int j = 0; j < 3; j++) {
            if (f[i][j] == 0)
                cout << "  ";
            else
                cout << f[i][j] << " ";
        }
        cout << "|\n";
    }
    cout << " +-------+\n";
}

// get position of number in field
void get_pos(int n, int *pos) {
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
            if (f[i][j] == n) {
                pos[0] = i;
                pos[1] = j;
                return;
            }
        }
    }
}

// check if finish sequenze is reached
bool is_finished() {
    int last = -1;
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 3; j++) {
            if (f[i][j] > last)
                last = f[i][j];
            else
                return false;
        }
        return (f[2][0] = 7 && f[2][1] == 8 && f[2][2] == 0);
    }
}

// getting highscore from file
// if file is not existent, it returns -1
// (= not set)
int get_highscore() {
    ifstream fr(HS_FILENAME);
    int out = -1;
    if (fr.good())
        fr >> out;
    return out;
}

// write highscore to file
void set_highscore(int m) {
    ofstream fw(HS_FILENAME);
    if (fw.good()) {
        fw << m;
        fw.close();
    }
}

// reset highscore by writing -1
// (= not set) to the high score file
void reset_highscore() {
    set_highscore(-1);
}

// just a function to check if an argument is
// set as start argument
bool arg_exists(char** begin, char** end, const string& option)
{
    return find(begin, end, option) != end;
}


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

    // checking for debug and reset start argument
    if (arg_exists(argv, argv + argc, "-d"))
        debug_mode = 1;
    if (arg_exists(argv, argv + argc, "-r"))
        reset_highscore();

    // get highscore
    highscore = get_highscore();

    int i = 0;

    // filling field with numbers randomly
    // if debug_mode is set, it will be filled
    // with a prepared structure which can be solved
    // with only one move
    if (!debug_mode) {
        while (i < 9) {
            int numbs[] = { 1,2,3,4,5,6,7,8,0 };
            int c_r[] = { rand() % 3, rand() % 3 };
            int *e = &f[c_r[0]][c_r[1]];
            if (*e == 0) {
                *e = numbs[i++];
            }
        }
    }
    else {
        int count = 1;
        for (int i = 0; i < 2; i++)
            for (int j = 0; j < 3; j++)
                f[i][j] = count++;
        f[2][0] = 7;
        f[2][1] = 0;
        f[2][2] = 8;
    }


    int inpt;

    do {
        print_field();

        cout << "\nEnter number (0 for exit) > ";
        cin >> inpt;

        // check if input is in bounds
        // else: ignore input
        if (inpt > 8 || inpt < 0)
            continue;

        int pos[2], free[2];
        // get grid position of input number
        // and free slot (0)
        get_pos(inpt, pos);
        get_pos(0, free);
        // calculate difference between the two points
        float diff = sqrt(
            (free[0] - pos[0]) * (free[0] - pos[0]) +
            (free[1] - pos[1]) * (free[1] - pos[1])
        );

        // If the difference is more than 1,
        // ignore input
        if (diff > 1)
            continue;

        // swap value of input position with
        // value of empty (0) position and
        // count up moves after
        int tmp = f[pos[0]][pos[1]];
        f[pos[0]][pos[1]] = f[free[0]][free[1]];
        f[free[0]][free[1]] = tmp;
        moves++;
    }
    // cancel with input 0 or if finished
    while (inpt != 0 && !is_finished());

    print_field();

    // just a check to dont print won text if
    // canceled with 0-input
    // else print won text, moves and save as
    // high score, if moves are less then the set
    // high score or if high score was not set before
    if (inpt != 0) {
        cout << "\nWon!\nCount of moves: " << moves << endl;
        if (moves < highscore || highscore == -1) {
            set_highscore(moves);
            cout << "Congratulation! You set a new highscore!\n";
        }
    }
}