LeetCode 419. Battleships in a Board

Given an 2D board, count how many different battleships are in it. The battleships are represented with ‘X’s, empty slots are represented with ‘.’s. You may assume the following rules:

You receive a valid board, made of only battleships or empty slots.
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.
In the above board there are 2 battleships.
Invalid Example:
This is an invalid board that you will not receive – as battleships will always have a cell separating between them.


分析:其实只需要数战列舰的头部有几个就行了,因为战列舰要么横着要么竖着,它的头部肯定满足以下条件:1.它的上方是空地(或者边界) 2.它的左方是空地(或者边界)


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