关于最近比较火的二叉树翻转的问题

这是我想当然写的代码，实际发现根本不行(在在新问答提交居然测试通过了，但是本地跑测试不行，难道是我 main 函数里面初始做得不对？).

struct TreeNode {
    int val;
    struct TreeNode* left;
    struct TreeNode* right;
};

struct TreeNode* invertTree(struct TreeNode* node){
    if(node == NULL){
        return node;
    }
    struct TreeNode* tmp = node->left;
    node->left = invertTree(node->right);
    node->right = invertTree(tmp);
    return node;
}
int main(){
    //        4
    //      /   \
    //     2     7
    //    / \   / \
    //   1   3 6   9

    struct TreeNode rootNode;
    struct TreeNode leftNode;
    struct TreeNode rightNode;

    struct TreeNode leftNode1;
    struct TreeNode leftNode2;

    struct TreeNode rightNode1;
    struct TreeNode rightNode2;


    leftNode1.val = 1;
    leftNode1.left = NULL;
    leftNode1.right = NULL;

    leftNode2.val = 3;
    leftNode2.left = NULL;
    leftNode2.right = NULL;

    leftNode.val = 2;
    leftNode.left = &leftNode1;
    leftNode.right = &leftNode2;

    rightNode1.val = 6;
    rightNode1.left = NULL;
    rightNode1.right = NULL;

    rightNode2.val = 9;
    rightNode2.left = NULL;
    rightNode2.right = NULL;

    rightNode.val = 7;
    rightNode2.left = &rightNode1;
    rightNode2.right = &rightNode2;

    rootNode.val = 4;
    rootNode.left = &leftNode;
    rootNode.right = &rightNode;

    invertTree(&rootNode);
}

编译能通过，执行就提示Segmentation fault: 11