[LeetCode] Number of Islands

 1 class Solution {
 2 public:
 3     void dfs(vector<vector<char>> &grid, int x, int y) {
 4         if (x < 0 || x >= grid.size()) return;
 5         if (y < 0 || y >= grid[0].size()) return;
 6         if (grid[x][y] != ‘1‘) return;
 7         grid[x][y] = ‘X‘;
 8         dfs(grid, x + 1, y);
 9         dfs(grid, x - 1, y);
10         dfs(grid, x, y + 1);
11         dfs(grid, x, y - 1);
12     }
13     
14     int numIslands(vector<vector<char>> &grid) {
15         if (grid.empty() || grid[0].empty()) return 0;
16         int N = grid.size(), M = grid[0].size();
17         int cnt = 0;
18         for (int i = 0; i < N; ++i) {
19             for (int j = 0; j < M; ++j) {
20                 if (grid[i][j] == ‘1‘) {
21                     dfs(grid, i, j);
22                     ++cnt;
23                 }
24             }
25         }
26         return cnt;
27     }
28 };