easy

import java.util.*;
public class b {

    static int [][] dirs = {{0,1},{1,0},{-1,0},{0,-1}};

    public static int maxTrees(int [][] matrix, int [][] fireStations, int [][] fires) {

        // [x, y]
        Queue<int[]> fireQ = new LinkedList<>();
        Queue<int[]> fireStationQ = new LinkedList<>();

        int N = matrix.length, M = matrix[0].length;

        boolean [][] visitedFire = new boolean [N][M];
        boolean [][] visitedStation = new boolean [N][M];

        int savedTrees = 0;
        for (int [] fireStation: fireStations) {
            int x = fireStation[0], y = fireStation[1];
            if (matrix[x][y] == -1) continue;
            savedTrees += matrix[x][y];
            visitedStation[x][y] = true;
            fireStationQ.add(fireStation);
        }

        for (int [] fire: fires) {
            matrix[fire[0]][fire[1]] = 0;
            visitedFire[fire[0]][fire[1]] = true;
            fireQ.add(fire);
        }


        while (!fireStationQ.isEmpty()) {

            int stations = fireStationQ.size();

            //stations have priority, process before fire step
            for (int i =0; i < stations;i++){
                int [] station = fireStationQ.poll();

                for (int [] dir : dirs) {
                    int x = station[0]+dir[0];
                    int y = station[1]+dir[1];

                    if (x >=0 && y >=0 && x < N && y <M && matrix[x][y] != -1 && !visitedStation[x][y]) {
                        visitedStation[x][y] = true;
                        savedTrees += matrix[x][y];
                        fireStationQ.add(new int [] { x,y});
                    }
                }
            }

            // assume fires can still spread after meeting firefighter
            int fireSize = fireQ.size();
            for (int i = 0; i < fireSize; i++){
                int [] fireCell = fireQ.poll();
                for (int [] dir : dirs) {
                    int x = fireCell[0]+dir[0];
                    int y = fireCell[1]+dir[1];
                    if (x >=0 && y >=0 && x < N && y < M && matrix[x][y] != -1 && !visitedFire[x][y]) {
                        visitedFire[x][y] = true;
                        matrix[x][y] = 0;
                        fireQ.add(new int [] { x,y});
                    }
                }
            }
        }

        return savedTrees;

    }