Invert Binary Tree

Problem

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

Constraints

• The number of nodes in the tree is in the range [0, 100].
• -100 <= Node.val <= 100

Solution

The problem Invert Binary Tree can be solved by recursively exchanging child nodes for every nodes.

Implementation

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution
{
  public:
    TreeNode *invertTree(TreeNode *root)
    {
        if (root == NULL)
            return root;

        TreeNode *temp = root->left;
        root->left = root->right;
        root->right = temp;

        invertTree(root->left);
        invertTree(root->right);
        return root;
    }
};