题解 | #岛屿数量# 没有真正的理解这题的本质。

class Solution {
public:
    /**
     * 判断岛屿数量
     * @param grid char字符型vector<vector<>> 
     * @return int整型
     */
    /*
     有一个为1的时候就被周边所有的1都置成0，就产生了隔离。有点像朋友圈。
    */
    void dfs(vector<vector<char> >& grid, int x, int y) {
        int column = grid.size(), line = grid[0].size();
        if (x < 0 || x >= column || y < 0 || y >= line) {
            return;
        }
        if (grid[x][y] == '0') {
            return;
        }
        grid[x][y] = '0';
        dfs(grid, x+1, y);
        dfs(grid, x-1, y);
        dfs(grid, x, y + 1);
        dfs(grid, x, y-1);
    }
    
    int solve(vector<vector<char> >& grid) {
        int column = grid.size(), line = grid[0].size();
        vector<vector<bool>> flag(column, vector<bool>(line, false));
        int cnt = 0;
        for (int i = 0; i < column; i++) {
            for (int j = 0; j < line; j++) {
                if (grid[i][j] == '1') {
                    cnt++;
                    dfs(grid, i, j);
                }
            }
        }
        return cnt;
        // write code here
    }
};