Blind 75 / Trees / Invert Binary Tree

Invert Binary Tree

EasyTrees
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Problem

Given the root of a binary tree, invert the tree by swapping every left and right child, and return the root.

Examples

Example 1
Input:root = [4,2,7,1,3,6,9]
Output:[4,7,2,9,6,3,1]
Example 2
Input:root = []
Output:[]

Constraints

  • The number of nodes is in the range [0, 100].

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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 ↗

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