public static List<String> bomberMan(int n, List<String> grid) {
    // Write your code here
    if(n==1){return grid;}
    if(n%2==0) {
        int length = grid.get(0).length();
        
        String oString = repeatChar('O', length);
        for(int i=0; i<grid.size(); i++){
            grid.set(i, oString);
        }
        return grid;
    }
    
    
    grid = switchStates(grid);
    if(n%4==3){return grid;}
    return switchStates(grid);
    
    }
    
    
    public static String repeatChar(char c, int times) {
        StringBuilder sb = new StringBuilder(times);
        for (int i = 0; i < times; i++) {
            sb.append(c);
        }
        return sb.toString();
    }
    
    // function to switch between the 2 states -
    // from seconds 3-7-11-15---n%4==3
    // to seconds 5-9-13-17---n%4==1
    public static List<String> switchStates(List<String> grid){
    char[][] charArray = new char[grid.size()][];

    for (int i = 0; i < grid.size(); i++) {
            charArray[i] = grid.get(i).toCharArray(); // Convert each String to a char[]
        }
    for(int i=0; i<grid.size(); i++){
      second: for(int j=0; j<charArray[0].length; j++){
          int[][] positions = {{i+1, j}, {i-1, j}, {i, j+1}, {i, j-1}};
          if (grid.get(i).charAt(j) == '.'){
              for(int[] pos : positions){
                  int x = pos[0];
                  int y = pos[1];
                  if(x>=0 && x < grid.size() && y >= 0 && y < charArray[0].length){
                      if(grid.get(x).charAt(y) == 'O'){
                          continue second;
                      }
                  }
              }
              charArray[i][j] = 'O';
          }
          else {
              
              charArray[i][j] = '.';
              for(int[] pos : positions){
                  int x = pos[0];
                  int y = pos[1];
                  if(x>=0 && x < grid.size() && y >= 0 && y < charArray[0].length){
                      charArray[x][y] = '.';
                  }
              } 
          }
      }  
    }
    for(int i =0 ; i < charArray.length; i++){
        String s = new String(charArray[i]);
        grid.set(i, s);
    }
    return grid;
    }