200. 岛屿数量

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