just compare number of rows and columns that has only 1 'B'

```
class Solution {
public int findLonelyPixel(char[][] picture) {
if(picture == null || picture.length == 0){return 0;}
int row = picture.length;
int col = picture[0].length;
int[] check_row = new int[row];
int count_row = 0;
int[] check_col = new int[col];
int count_col = 0;
for(int i = 0; i < row; i++){
for(int j = 0; j < col; j++){
if(picture[i][j] == 'B'){
check_row[i] += 1;
if(check_row[i] == 1){count_row++;}
if(check_row[i] == 2){count_row--;}
check_col[j] += 1;
if(check_col[j] == 1){count_col++;}
if(check_col[j] == 2){count_col--;}
}
}
}
return Math.min(count_row,count_col);
}
}
```