题解 | #岛屿数量#

#include <vector>

class Solution {
  public:
    void dfs(vector<vector<char>>& grid, int row, int col) {
        if (row < 0 || row >= grid.size() || col < 0 || col >= grid[0].size() ||
                grid[row][col] == '0') {
            return;
        }

        grid[row][col] = '0'; // 标记当前位置为已访问过

        // 检查上下左右四个方向
        dfs(grid, row - 1, col);
        dfs(grid, row + 1, col);
        dfs(grid, row, col - 1);
        dfs(grid, row, col + 1);
    }

    int solve(vector<vector<char>>& grid) {
        int m = grid.size();
        if (m == 0) {
            return 0;
        }
        int n = grid[0].size();

        int numIslands = 0;
        for (int row = 0; row < m; ++row) {
            for (int col = 0; col < n; ++col) {
                if (grid[row][col] == '1') {
                    ++numIslands;
                    dfs(grid, row,
                        col); // 将当前岛屿的所有相邻陆地标记为已访问过
                }
            }
        }

        return numIslands;
    }
};