Anna.cpp

#include "Anna.h"
#include <bits/stdc++.h>
using namespace std;

void Anna(int n, int k, vector<int> ys, vector<int> xs) {
    vector<pair<int, int>> dirs = {{-1, -1}, {-1, 0}, {-1, 1}, {0, -1}, {0, 0}, {0, 1}, {1, -1}, {1, 0}, {1, 1}};

    vector<bool> uses(9, 0);
    for (int j = 0; j < k; ++j) {
        int x = j % 3;
        int y = j / 3;
        int dy = (ys[j] + 3 - y + 1) % 3;
        int dx = (xs[j] + 3 - x + 1) % 3;
        uses[3*dy + dx] = 1;
    }
    int unused = 0;
    while(uses[unused]) ++unused;

    for (int y = 0; y < n; ++y) {
        for (int x = 0; x < n; ++x) {
            int ind = 3 * (y % 3) + (x % 3);
            if (ind == 8) {
                SetFlag(y, x, 1); // Calibration flag
            } else if (ind == 7) {
                SetFlag(y, x, 2 + unused); // Unused flag
            } else if (ind < k) {
                if (ys[ind] < y - 1) SetFlag(y, x, 2);
                else if (ys[ind] > y + 1) SetFlag(y, x, 3);
                else if (xs[ind] < x - 1) SetFlag(y, x, 4);
                else if (xs[ind] > x + 1) SetFlag(y, x, 5);
                else {
                    for (int j = 0; j < 9; ++j) {
                        if (ys[ind] == y + dirs[j].first && xs[ind] == x + dirs[j].second) {
                            SetFlag(y, x, 6 + j - (bool)(j >= unused));
                        }
                    }
                }
            } else {
                SetFlag(y, x, 2); // only happens if k < 7
            }
        }
    }
}