No need to modify the input matrix.

```
public int countBattleships(char[][] board) {
int count = 0;
for(int i=0;i<board.length;i++)
for(int j=0;j<board[0].length;j++)
if(board[i][j]=='X' && (i==0 || board[i-1][j]!='X') && (j==0 || board[i][j-1]!='X')) count++;
return count;
}
```