Question

Formatted question description: https://leetcode.ca/all/1485.html

 1485. Clone Binary Tree With Random Pointer

 A binary tree is given such that each node contains an additional random pointer which could point to any node in the tree or null.

 Return a deep copy of the tree.

 The tree is represented in the same input/output way as normal binary trees where each node is represented as a pair of [val, random_index] where:

     val: an integer representing Node.val
     random_index: the index of the node (in the input) where the random pointer points to, or null if it does not point to any node.

 You will be given the tree in class Node and you should return the cloned tree in class NodeCopy.
 NodeCopy class is just a clone of Node class with the same attributes and constructors.


 Example 1:

 Input: root = [[1,null],null,[4,3],[7,0]]
 Output: [[1,null],null,[4,3],[7,0]]
 Explanation: The original binary tree is [1,null,4,7].
 The random pointer of node one is null, so it is represented as [1, null].
 The random pointer of node 4 is node 7, so it is represented as [4, 3] where 3 is the index of node 7 in the array representing the tree.
 The random pointer of node 7 is node 1, so it is represented as [7, 0] where 0 is the index of node 1 in the array representing the tree.


 Example 2:

 Input: root = [[1,4],null,[1,0],null,[1,5],[1,5]]
 Output: [[1,4],null,[1,0],null,[1,5],[1,5]]
 Explanation: The random pointer of a node can be the node itself.


 Example 3:

 Input: root = [[1,6],[2,5],[3,4],[4,3],[5,2],[6,1],[7,0]]
 Output: [[1,6],[2,5],[3,4],[4,3],[5,2],[6,1],[7,0]]


 Example 4:

 Input: root = []
 Output: []


 Example 5:

 Input: root = [[1,null],null,[2,null],null,[1,null]]
 Output: [[1,null],null,[2,null],null,[1,null]]


 Constraints:

     The number of nodes in the tree is in the range [0, 1000].
     Each node's value is between [1, 10^6].

Algorithm

Using HashMap to record, those nodes have been visited, because there are random nodes, it may be repeated first.

Code

Java

public class Clone_Binary_Tree_With_Random_Pointer {

    class Solution_bfs {
        public NodeCopy copyRandomBinaryTree(Node root) {
            // normal case
            if (root == null) {
                return null;
            }

            // normal case
            HashMap<Node, NodeCopy> map = new HashMap<>();
            map.put(root, new NodeCopy(root.val));
            Queue<Node> queue = new LinkedList<>();
            queue.add(root);
            while (!queue.isEmpty()) {
                Node node = queue.poll();
                NodeCopy newNode = map.get(node);
                if (node.random != null) {
                    if (!map.containsKey(node.random)) {
                        map.put(node.random, new NodeCopy(node.random.val));
                    }
                    newNode.random = map.get(node.random);
                }
                if (node.left != null) {
                    if (!map.containsKey(node.left)) {
                        map.put(node.left, new NodeCopy(node.left.val));
                    }
                    newNode.left = map.get(node.left);
                    queue.add(node.left);
                }
                if (node.right != null) {
                    if (!map.containsKey(node.right)) {
                        map.put(node.right, new NodeCopy(node.right.val));
                    }
                    newNode.right = map.get(node.right);
                    queue.add(node.right);
                }
            }

            return map.get(root);
        }
    }


    class Solution_dfs {

        HashMap<Node, NodeCopy> map = new HashMap<>();

        public NodeCopy copyRandomBinaryTree(Node root) {
            // corner case
            if (root == null) {
                return null;
            }

            // normal case
            if (map.containsKey(root)) {
                return map.get(root);
            }

            NodeCopy copy = new NodeCopy(root.val);
            map.put(root, copy);

            copy.left = copyRandomBinaryTree(root.left);
            copy.right = copyRandomBinaryTree(root.right);
            copy.random = copyRandomBinaryTree(root.random);

            return copy;
        }
    }

    class NodeCopy {
        int val;
        NodeCopy left;
        NodeCopy right;
        NodeCopy random;
        NodeCopy(int val) { this.val = val; }
    }

    class Node {
        int val;
        Node left;
        Node right;
        Node random;
        Node() {}
        Node(int val) { this.val = val; }
        Node(int val, Node left, Node right, Node random) {
            this.val = val;
            this.left = left;
            this.right = right;
            this.random = random;
        }
    }
}

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