Serialize and Deserialize Binary Tree
Design an algorithm to serialize a binary tree to a string and deserialize it back.
Input: level-order array (comma-separated, 'null' for missing). Output: serialized then deserialized back to level-order.
Example:
1,2,3,null,null,4,5
1 2 3 null null 4 5
- The input string
1,2,3,null,null,4,5is first split into an array of node values, representing a level-order traversal of the binary tree. - A binary tree is constructed from this array, where
nullvalues indicate missing nodes:- Root node: 1
- Left child of 1: 2
- Right child of 1: 3
- Left child of 2: null
- Right child of 2: null
- Left child of 3: 4
- Right child of 3: 5
- The tree is then serialized to a string, which in this case is the same as the input string since the serialization is based on level-order traversal.
- The serialized string is then deserialized back to a binary tree, resulting in the same tree structure as before.
- The final output is obtained by performing a level-order traversal of the deserialized tree, resulting in
1 2 3 null null 4 5.
Constraints:
- 0 <= number of nodes <= 10^4
- -1000 <= Node.val <= 1000
Background Knowledge
The problem of serializing and deserializing a binary tree involves converting the tree into a linear data structure, such as a string, and then reconstructing the original tree from this string. To understand this problem, it's essential to have a solid grasp of binary tree data structures, including their node composition and traversal methods. A binary tree is a hierarchical data structure where each node has at most two children, referred to as the left child and the right child.
Key concepts in binary trees include level-order traversal, which visits nodes level by level from left to right, and pre-order, in-order, and post-order traversal methods, which visit nodes in different orders based on their position relative to their children. Understanding these traversal methods is crucial for serializing the tree, as they dictate the order in which nodes are visited and added to the serialized string. Additionally, familiarity with queue data structures is necessary for implementing level-order traversal.
Serialization and deserialization also involve string manipulation and parsing, as the serialized tree is represented as a string and must be parsed to reconstruct the original tree. This process requires careful consideration of how to represent null or missing nodes in the serialized string, to ensure that the deserialized tree accurately reflects the structure of the original tree.
Algorithm/Approach
The general approach to solving this problem involves using a level-order traversal to serialize the binary tree, as this method visits nodes in a predictable and consistent order. The algorithm will utilize a queue data structure to keep track of nodes to be visited and a string to build the serialized representation of the tree. For deserialization, the algorithm will parse the serialized string and use the parsed information to reconstruct the original tree, likely using a recursive approach or iterative method with a queue.
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