Leetcode 200. Number of Islands

 1 class Solution {
 2 public:
 3     int numIslands(vector<vector<char>>& grid) {
 4         int many = 0;
 5         if(grid.empty() || grid[0].empty())
 6             return many;
 7         //void dfs(vector<vector<char>> &grid,int i, int j, int n, int m);
 8         int n = grid.size();
 9         int m = grid[0].size();
10         for(int i = 0; i < n; i++){
11             for(int j = 0; j < m; j++){
12                 if(grid[i][j] == ‘1‘){
13                     dfs(grid,i,j,n,m);
14                     many++;
15                 }
16             }
17         }
18         return many;
19     }
20     void dfs(vector<vector<char>>& grid,int i, int j, int n, int m)
21     {
22         grid[i][j] = ‘0‘;
23         if((i-1) >= 0 && grid[i-1][j] == ‘1‘)
24             dfs(grid, i-1, j, n, m);
25         if((i+1) < n && grid[i+1][j] == ‘1‘)
26             dfs(grid, i+1, j, n, m); 
27         if((j-1) >= 0 && grid[i][j-1] == ‘1‘)
28             dfs(grid, i, j-1, n, m);
29         if((j+1) < m && grid[i][j+1] == ‘1‘)
30             dfs(grid, i, j+1, n, m);
31     }
32 };