Coder's Cat

LeetCode: Clone Binary Tree With Random Pointer

2020-07-15

Recursive algorithms with a map for ‘Clone Binary Tree With Random Pointer’

file:img/CAPTURE-2020_07_15_clone-binary-tree-with-random-pointer.org_20200715_113620.png

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;
}
};