200. Number of Islands

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