feat(ml): $200.number-of-islands.md (#433)

Author: ztianming

problems/200.number-of-islands.md

@@ -64,7 +64,46 @@ Output: 3
 
 ## 代码
 
-* 语言支持：JS, python3，Java
+* 语言支持：C++, Java, JS, python3
+
+
+C++ Code：
+
+```c++
+class Solution {
+public:
+    int numIslands(vector<vector<char>>& grid) {
+        int res = 0;
+        for(int i=0;i<grid.size();i++)
+        {
+            for(int j=0;j<grid[0].size();j++)
+            {
+                if(grid[i][j] == '1')
+                {
+                    dfs(grid, i, j);
+                    res += 1;
+                }
+            }
+        }
+        return res;
+
+    }
+    void dfs(vector<vector<char>>& grid, int i, int j)
+    {
+        // edge
+        if(i<0 || i>= grid.size() || j<0 || j>= grid[0].size() || grid[i][j] != '1')
+        {
+            return;
+        }
+        grid[i][j] = '0';
+        dfs(grid, i+1, j);
+        dfs(grid, i-1, j);
+        dfs(grid, i, j+1);
+        dfs(grid, i, j-1);
+    }
+};
+
+```
 
 Java Code：