419. Battleships in a Board

The key to solve this problem is the following two conditions:

- Battleships can only be placed horizontally or vertically. In other words, they can only be made of the shape 1xN (1 row, N columns) or Nx1 (N rows, 1 column), where N can be of any size.

- At least one horizontal or vertical cell separates between two battleships - there are no adjacent battleships.

So the problem becomes something similar to counting islands where islands here is 'X's surrounded by '.'.

1:  class Solution {  
2:  public:  
3:    int countBattleships(vector<vector<char>>& board) {  
4:      int count = 0;  
5:      for (int i = 0; i < board.size(); i++) {  
6:        for (int j = 0; j < board[0].size(); j++) {  
7:          if (board[i][j] == 'X' && (i == 0 || board[i-1][j] != 'X') && (j == 0 || board[i][j-1] != 'X')) count++;  
8:        }  
9:      }  
10:      return count;  
11:    }  
12:  };