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 (i.e., there are no adjacent battleships).
Example 1:
X _ _ X
_ _ _ X
_ _ _ X
_ _ _ _
Input: board = [["X",".",".","X"],[".",".",".","X"],[".",".",".","X"]]
Output: 2
Example 2:
Input: board = [["."]]
Output: 0
Constraints:
m == board.length
n == board[i].length
1 <= m, n <= 200
board[i][j]
is either'.'
or'X'
.
Follow up: Could you do it in onepass, using only O(1)
extra memory and without modifying the values board
?
Find all the topleft corners of the ships

