Battleships in a Board
Given an m x n matrix board where each cell is a battleship 'X' or empty '.', return the number of the battleships on board.
Battleships can only be placed horizontally or vertically on board. In other words, they can only be made of the shape 1 x k (1 row, k columns) or k x 1 (k rows, 1 column), where k can be of any size. At least one horizontal or vertical cell separates between two battleships, so there are no adjacent battleships.
Follow up: Could you do it in one-pass, using only O(1) extra memory and without modifying the values board?
Example 1
X . . X . . . X . . . X
Input
board = [["X",".",".","X"],[".",".",".","X"],[".",".",".","X"]]Output
2There are two battleships: one single-cell ship in the top-left and one vertical ship in the rightmost column.
Example 2
.
Input
board = [["."]]Output
0The board contains no battleship cells.
Constraints
- m == board.length
- n == board[i].length
- 1 <= m, n <= 200
- board[i][j] is either
'.'or'X'.