题解 | #岛屿数量#

class Solution
{
public:
    void dfs(vector<vector<char>> &grid, int r, int c)
    {
        int rows = grid.size();
        int cols = grid[0].size();

        // 边界检查
        if (r < 0 || c < 0 || r >= rows || c >= cols || grid[r][c] == '0')
            return;

        grid[r][c] = '0';

        dfs(grid, r - 1, c); // 上
        dfs(grid, r + 1, c); // 下
        dfs(grid, r, c - 1); // 左
        dfs(grid, r, c + 1); // 右
    }

    int solve(vector<vector<char>> &grid)
    {
        int rows = grid.size();
        if (rows == 0)
            return 0;
        int cols = grid[0].size();
        int island_num = 0;

        // 逐个格子进行检查
        for (int i = 0; i < rows; ++i)
            for (int j = 0; j < cols; ++j)
                if (grid[i][j] == '1')
                {
                    dfs(grid, i, j);
                    island_num++;
                }

        return island_num;
    }
};