Leetcode no. 200

最新推荐文章于 2024-08-04 10:33:51 发布

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最新推荐文章于 2024-08-04 10:33:51 发布

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本文介绍了一种用于计算二维网格中岛屿数量的算法。该算法通过遍历每个网格单元，并使用递归搜索来标记已访问过的陆地，从而实现对岛屿数量的有效计数。文章提供了完整的Java代码实现。

200. Number of Islands

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.

Example 1:

Answer: 1

Example 2:

Answer: 3

public class Solution {
    public int numIslands(char[][] grid) {
        if (grid.length==0 || grid[0].length==0) return 0;
        int count=0;
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[0].length; j++) {
                if (grid[i][j]=='1') {
                    search(grid,i,j);
                    count++;
                }
            }
        }
        return count;
    }
    private void search(char[][] grid, int row, int col){
        if (row<0 || col<0 || row>=grid.length || col>=grid[0].length || grid[row][col]!='1')
            return;
        grid[row][col]= '0';
        search(grid, row+1, col);
        search(grid, row-1, col);
        search(grid, row, col+1);
        search(grid, row, col-1);
    }
}