MaxAreaOfIsland.py

# -*- coding: utf-8 -*-
# @File    : MaxAreaOfIsland.py
# @Date    : 2020-03-07
# @Author  : tc
"""
题号 695. 岛屿的最大面积
给定一个包含了一些 0 和 1的非空二维数组 grid,一个岛屿是由四个方向 (水平或垂直)的1 (代表土地)构成的组合。你可以假设二维矩阵的四个边缘都被水包围着。

找到给定的二维数组中最大的岛屿面积。(如果没有岛屿，则返回面积为0。)

示例 1:

[[0,0,1,0,0,0,0,1,0,0,0,0,0],
 [0,0,0,0,0,0,0,1,1,1,0,0,0],
 [0,1,1,0,1,0,0,0,0,0,0,0,0],
 [0,1,0,0,1,1,0,0,1,0,1,0,0],
 [0,1,0,0,1,1,0,0,1,1,1,0,0],
 [0,0,0,0,0,0,0,0,0,0,1,0,0],
 [0,0,0,0,0,0,0,1,1,1,0,0,0],
 [0,0,0,0,0,0,0,1,1,0,0,0,0]]
对于上面这个给定矩阵应返回 6。注意答案不应该是11，因为岛屿只能包含水平或垂直的四个方向的‘1’。

示例 2:

[[0,0,0,0,0,0,0,0]]
对于上面这个给定的矩阵, 返回 0。

注意: 给定的矩阵grid 的长度和宽度都不超过 50。

和第200题岛屿数量类似

参考：https://leetcode.com/problems/max-area-of-island/discuss/108541/easy-python

"""
from typing import List

class Solution:
    def maxAreaOfIsland(self, grid: List[List[int]]) -> int:
        m,n = len(grid),len(grid[0])

        def dfs(i,j):
            if 0 <= i < m and 0 <= j < n and grid[i][j]:
                grid[i][j] = 0
                return 1 + dfs(i-1,j) + dfs(i+1,j) + dfs(i,j+1) + dfs(i,j-1)
            return 0
        areas = [dfs(i,j) for i in range(m) for j in range(n) if grid[i][j]]
        return max(areas) if areas else 0


if __name__ == '__main__':
    grid = [[0,0,1,0,0,0,0,1,0,0,0,0,0],
             [0,0,0,0,0,0,0,1,1,1,0,0,0],
             [0,1,1,0,1,0,0,0,0,0,0,0,0],
             [0,1,0,0,1,1,0,0,1,0,1,0,0],
             [0,1,0,0,1,1,0,0,1,1,1,0,0],
             [0,0,0,0,0,0,0,0,0,0,1,0,0],
             [0,0,0,0,0,0,0,1,1,1,0,0,0],
             [0,0,0,0,0,0,0,1,1,0,0,0,0]]

    solution = Solution()
    print(solution.maxAreaOfIsland(grid))