CountUnGuarded.java

//2257. Count Unguarded Cells in the Grid

class Solution {
    public int countUnguarded(int m, int n, int[][] guards, int[][] walls) {
        int[][] grid = new int[m][n];
        for(int[] wall : walls){
            grid[wall[0]][wall[1]] = 1;
        }
        for(int[] guard : guards){
            grid[guard[0]][guard[1]] = 2;
        }

        int[][] dirs =  {{-1,0},{1,0},{0,-1},{0,1}};
        for(int[] guard : guards){
            int r = guard[0];
            int c = guard[1];
            for(int[] d : dirs){
                int nr = r + d[0];
                int nc = c + d[1];
                while(nr >= 0 && nr<m && nc<n && nc >= 0 && grid[nr][nc] != 1 && grid[nr][nc] != 2){
                    if(grid[nr][nc] == 0){
                        grid[nr][nc] = 3;
                    }
                    nr += d[0];   
                    nc += d[1];
                }
            }
        }

        int count = 0;
        for (int i=0; i<m; i++){
            for(int j=0; j<n; j++){
                if(grid[i][j] == 0){
                    count++;
                }
            }
        }
        return count;
    }
}