leetcode-----200. 岛屿数量

• 链接：https://leetcode-cn.com/problems/number-of-islands/

// flood fill

class Solution {
public:
    vector<vector<char>> g;
    int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};

    void dfs(int x, int y) {
        g[x][y] =0;
        for (int i = 0; i < 4; ++i) {
            int a = x + dx[i], b = y + dy[i];
            if (a >= 0 && a < g.size() && b >= 0 && b < g[a].size() && g[a][b] == '1') {
                dfs(a ,b);
            }
        }
    }

    int numIslands(vector<vector<char>>& _g) {
        g = _g;
        int cnt = 0;
        for (int i = 0; i < g.size(); ++i) {
            for (int j = 0; j < g[i].size(); ++j) {
                if (g[i][j] == '1') {
                    dfs(i, j);
                    cnt++;
                }
            }
        }
        return cnt;
    }
};