## Monday, May 16, 2022

### Easy_Question5 : Invert Binary Tree

Given the root of a binary tree, invert the tree, and return its root.

Example 1:

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


Example 2:

Input: root = [2,1,3]
Output: [2,3,1]


Example 3:

Input: root = []
Output: []


Constraints:

• The number of nodes in the tree is in the range
class Solution {
public TreeNode invertTree(TreeNode root) {
if (root == null) return null;
while (!queue.isEmpty()) {
TreeNode current = queue.poll();
TreeNode temp = current.left;
current.left = current.right;
current.right = temp;
}
return root;
}
}

Complexity Analysis

Since each node in the tree is visited/added to the queue only once, the time complexity is $O(n)$, where $n$ is the number of nodes in the tree.

Space complexity is $O(n)$, since in the worst case, the queue will contain all nodes in one level of the binary tree. For a full binary tree, the leaf level has $\lceil \frac{n}{2}\rceil=O(n)$ leaves.

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