Decode the Coding Interview in Ruby: Real-World Examples/

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Invert Binary Tree

Invert Binary Tree

Understand and solve the interview question "Invert Binary Tree".

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Description

In this lesson, your task is to invert a given a binary tree, T.

Let’s look at an example below:

Coding exercise

main.rb
TreeNode.rb
require './TreeNode.rb'
def invert_tree(root)
end
Invert binary tree

Solution

We can solve this problem using depth-first search (DFS).

The inverse of an empty tree is the empty tree. To invert tree T with root and subtrees left and right, we keep root the same and invert the right and left subtrees.

Let’s review the implementation below:

main.rb
TreeNode.rb
require './TreeNode.rb'
def invert_tree(root) 
    if root == nil  
      return root
    end
    
    right = invert_tree(root.right);
    left = invert_tree(root.left);
    root.left = right;
    root.right = left;
    return root;
end
# Driver Code
root = TreeNode.new(1)
root.left = TreeNode.new(2)
root.right = TreeNode.new(3)
root.left.left = TreeNode.new(4)
root.left.right = TreeNode.new(5)
root.right.left = TreeNode.new(6)
root.right.right = TreeNode.new(7)
print_tree(invert_tree(root))
Invert binary tree

Complexity measures

Time Complexity Space Complexity
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