695. Max Area of Island

最新推荐文章于 2022-05-13 15:04:41 发布

xdhc304

最新推荐文章于 2022-05-13 15:04:41 发布

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分类专栏： leetcode 文章标签： leetcode-java

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本文介绍了一个寻找二维数组中最大岛屿面积的算法实现。通过遍历矩阵并使用深度优先搜索(DFS)来计算每个由1组成的岛屿面积，最终返回最大的岛屿面积。文章提供了完整的Java代码示例。

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Given a non-empty 2D array grid of 0’s and 1’s, 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.

Find the maximum area of an island in the given 2D array. (If there is no island, the maximum area is 0.)

Example 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]]

Given the above grid, return 6. Note the answer is not 11, because the island must be connected 4-directionally.
Example 2:

[[0,0,0,0,0,0,0,0]]

Given the above grid, return 0.
Note: The length of each dimension in the given grid does not exceed 50.

class Solution {
    public int maxAreaOfIsland(int[][] grid) {    
        int max_air=0;  
        for(int i = 0;i < grid.length;i++){  
            for(int j = 0;j < grid[0].length;j++){  
                if(grid[i][j] == 1) max_air = Math.max(max_air,maxair(grid,i,j));  
            }  
        }  
        return max_air;  
    }  

    public int maxair(int[][] grid,int i,int j){  
        if(i >= 0 && i < grid.length && j >= 0 && j < grid[0].length && grid[i][j] == 1){  
            grid[i][j] = 0;  
            return 1 + maxair(grid,i+1,j) + maxair(grid,i-1,j) + maxair(grid,i,j+1) + maxair(grid,i,j-1);  
        }  
        return 0;  
    }  
}