Leetcode 226. Flip binary tree

subject

Give you the root node of a binary tree root , Flip this binary tree , And return its root node .

Ideas

• The first sequence traversal , First swap the left and right child nodes
• Then recursively exchange left and right subtrees

Code

/** * 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) {
    
        //  Recursive export 
        if(root == NULL) return root;

        //  The first sequence traversal   First swap the left and right child nodes   Then flip the left subtree and the right subtree 
        swap(root->left,root->right);
        invertTree(root->left);
        invertTree(root->right);
        return root;
    }
};