LeetCode 200. Number of Islands-优快云博客

本文介绍了一个基于深度优先搜索（DFS）算法解决的经典问题——计算二维网格中岛屿的数量。通过遍历每个网格单元并使用DFS标记相连的陆地，最终得出岛屿总数。

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

大致题意

找出岛屿的数量（1表示陆地）

题解

题目类型：dfs

我们遇到 1 便开始dfs消除关联的陆地，并返回岛屿的大小，如果该岛屿有大小，证明其存在（消除之后算不存在），count + 1

代码如下

class Solution {
public:
    int numIslands(vector<vector<char>>& grid) {
        int count = 0;
        for (int i = 0; i < grid.size(); i++) {
            for (int j = 0; j < grid[i].size(); j++) {
                if (search(i, j, grid)) {
                    count ++;
                }
            }
        }
        return count;
    }
    int search(int row, int column, vector<vector<char>>& grid) {
        if (row >= 0 && column >= 0 && row < grid.size() && column < grid[row].size() && grid[row][column] == '1') {
            grid[row][column] = '0';
            return 1 + search(row + 1, column, grid) + search(row - 1, column, grid) + search(row, column + 1, grid) + search(row, column - 1, grid);
        }
        return 0;
    }
};