695. Max Area of Island

Medium (Trung bình) Python 🔗 Xem trên LeetCode

📋 Đề Bài

You are given an m x n binary matrix grid. An island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.

The area of an island is the number of cells with a value 1 in the island.

Return the maximum area of an island in grid. If there is no island, return 0.

Example 1:

Input: 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]]
Output: 6
Explanation: The answer is not 11, because the island must be connected 4-directionally.

Example 2:

Input: grid = [[0,0,0,0,0,0,0,0]]
Output: 0

Constraints:

m == grid.length
n == grid[i].length
1 <= m, n <= 50
grid[i][j] is either 0 or 1.

🧠 Thuật Toán & Kỹ Thuật

DFS (Tìm kiếm theo chiều sâu)Matrix (Ma trận)

⏱️ Thời gian O(V+E)

💾 Không gian O(V)

💻 Lời Giải

Python 0695-max-area-of-island.py

class Solution:
    def maxAreaOfIsland(self, grid: List[List[int]]) -> int:
        maxArea = 0
        n, m = len(grid), len(grid[0])
        
        def dfs(x: int, y: int) -> int:
            if x < 0 or x == n or y < 0 or y == m or grid[x][y] == 0:
                return 0
            grid[x][y] = 0
            return 1 + dfs(x - 1, y) + dfs(x + 1, y) + dfs(x, y + 1) + dfs(x, y - 1)
        
        for i in range(n):
            for j in range(m):
                if grid[i][j] == 1:
                    maxArea = max(maxArea, dfs(i, j))
                    
        return maxArea