Only count an 'X' if there is no other to its left or above it. This means it's the first 'X' of a horizontal or vertical ship.

```
int countBattleships(vector<vector<char>>& board) {
if (board.empty() || board[0].empty()) return 0;
int res = 0;
for (int i = 0; i < board.size(); ++i) {
for (int j = 0; j < board[0].size(); ++j) {
bool left = i > 0 && board[i-1][j] == 'X';
bool up = j > 0 && board[i][j-1] == 'X';
res += board[i][j] == 'X' && !up && !left;
}
}
return res;
}
```