Number of Islands

最新推荐文章于 2025-05-07 17:27:01 发布

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本文介绍了一种计算二维网格地图中岛屿数量的方法。通过遍历网格并使用深度优先搜索，可以有效识别并计数被水包围的陆地区域。实例展示了如何应用此算法解决实际问题。

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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

与上一题的解决思路是类似的，如果是1，上下左右遍历，是1则置为0.

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