LeetCode //C - 226. Invert Binary Tree

226. 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 [0, 100].
• -100 <= Node.val <= 100

From: LeetCode
Link: 226. Invert Binary Tree

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Solution:

Ideas：

This function checks if the current node is NULL and, if not, it proceeds to swap the left and right child nodes. Then it recursively calls itself for the left and right children, which continues the process down the tree until all nodes have been visited and their children swapped.

Code:

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */

struct TreeNode* invertTree(struct TreeNode* root) {
    if (root == NULL) {
        return NULL;
    }
    
    // Swap the left and right children
    struct TreeNode* temp = root->left;
    root->left = root->right;
    root->right = temp;
    
    // Recursively invert the subtrees
    invertTree(root->left);
    invertTree(root->right);
    
    return root;
}