java 岛屿的最大面积(沉岛方法) leetcode题

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#leetcode #java #算法

这是一个关于寻找二维数组（代表岛屿）中最大岛屿面积的问题。算法通过遍历数组，遇到1（代表陆地）时，使用深度优先搜索（DFS）递归地访问相邻的陆地，并在遍历过程中更新最大岛屿面积。最终返回的是整个数组中最大的岛屿面积。

输入：

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]]

思路
1、遍历二维数组
2、遇到1，记录，将1改为0防止多记
3、递归步骤2

遍历二维数组

		int max = 0;
		
        for(int i = 0;i < grid.length;i++){
            
            for(int j = 0; j < grid[0].length;j++){

                if(grid[i][j] == 1){

                    max = Math.max(serach(grid,i,j),max);
                }
            }
        }

查找方法

    public int serach(int grid[][],int i,int j){

        if(i < 0 || i >= grid.length || j < 0 || j >= grid[0].length || grid[i][j] == 0){
            return 0;
        }

		//将1改为0
        grid[i][j] = 0;
        int num = 1;

        num += serach(grid,i-1,j);
        num += serach(grid,i+1,j);
        num += serach(grid,i,j-1);
        num += serach(grid,i,j+1);

        return num;
    }

源代码

    public int maxAreaOfIsland(int[][] grid) {

        int max = 0;

        for(int i = 0;i < grid.length;i++){
            
            for(int j = 0; j < grid[0].length;j++){

                if(grid[i][j] == 1){

                    max = Math.max(serach(grid,i,j),max);
                }
            }
        }

        return max;
    }

    public int serach(int grid[][],int i,int j){

        if(i < 0 || i >= grid.length || j < 0 || j >= grid[0].length || grid[i][j] == 0){
            return 0;
        }

        grid[i][j] = 0;
        int num = 1;

        num += serach(grid,i-1,j);
        num += serach(grid,i+1,j);
        num += serach(grid,i,j-1);
        num += serach(grid,i,j+1);

        return num;
    }