leetcode daily question

https://leetcode.cn/problems/invert-binary-tree/submissions/

Our idea for this topic is actually very simple. When encountering a null pointer, we have to return a null pointer because it needs to be exchanged. But there is a small detail here, that is, we save its left and right nodes. Our function interface here has a return value. , we save the currently returned recursive left tree or right tree. At this time, the root is their parent node for exchange. Let’s look at the code.

struct TreeNode* invertTree(struct TreeNode* root) {
    if(root == NULL)
    {
        return NULL;
    }
    struct TreeNode* left = invertTree(root->left);
    struct TreeNode* right = invertTree(root->right);
    root->left = right;
    root->right = left;
    return root;

}

Let's see what a recursively expanded graph looks like.

You may have a better understanding by looking at this picture. Here we have also drawn the nodes that store positions 1 and 3 and exchanged them. You can also try to draw them. This is what we will share today.