Serialize And Deserialize Binary Tree

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Problem

Design an algorithm to serialize a binary tree into a string, and deserialize that string back into a tree with the exact same structure and node values as the original.

Examples

Example 1

Input:root = [1,2,3,null,null,4,5]

Output:[1,2,3,null,null,4,5]

deserialize(serialize(root)) reproduces the original tree.

Example 2

Input:root = []

Output:[]

Constraints

The number of nodes is in the range [0, 10^4].

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How to approach it: the Trees pattern

A tree is a hierarchical structure where each node has at most a fixed number of children (two, for binary trees). Almost every tree problem reduces to a traversal — decide what order you visit nodes in, and what you do at each one.

Look for this pattern when

The problem is naturally recursive: "the answer for this tree depends on the answer for its subtrees."
You need level-by-level information (BFS) versus depth-first structural information (DFS).

Read the full Trees guide →

Video walkthroughs

Original problem on LeetCode ↗