## Deep copy

Deep copy is a process in which the copying process occurs recursively. We need to clone all the elements of a tree.

## Solution

The overall algorithm is recursive, but we need to find the previous cloned elements. So use a `hashmap`

will help us to store the pair relationship of the elements of source tree and the new cloned elements.

```
class Solution {
public:
map<Node*, NodeCopy*> node_map;
NodeCopy* copyRandomBinaryTree(Node* root) {
if(root == NULL) return NULL;
return dfs(root);
}
NodeCopy* dfs(Node* cur) {
if(cur == NULL) return NULL;
if(node_map.count(cur))
return node_map[cur];
NodeCopy* node = new NodeCopy(cur->val);
node_map[cur] = node;
node->left = dfs(cur->left);
node->right = dfs(cur->right);
node->random = dfs(cur->random);
return node;
}
};
```