Invert Binary Tree

Easy

Python

def invert_tree(root):
    if not root: return None
    root.left,root.right=invert_tree(root.right),invert_tree(root.left)
    return root

Java

public TreeNode invertTree(TreeNode root){
    if(root==null) return null;
    TreeNode tmp=root.left;
    root.left=invertTree(root.right);
    root.right=tmp;
    return root;
}

Key Insight

Simultaneous assignment swaps without temp. Java needs temp variable.

Python → Java Differences

Simultaneous swap vs temp variable
'not root' vs null check
Same recursive approach

Python

def invert_tree(root):
    if not root: return None
    root.left,root.right=invert_tree(root.right),invert_tree(root.left)
    return root

Java

public TreeNode invertTree(TreeNode root){
    if(root==null) return null;
    TreeNode tmp=root.left;
    root.left=invertTree(root.right);
    root.right=tmp;
    return root;
}

Algorithm Steps

1. Recursively invert
2. Swap children

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