代码实现：

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     struct TreeNode *left;*     struct TreeNode *right;* };*/void convertBiNode_pro(struct TreeNode *root, struct TreeNode **p) {if (root) {convertBiNode_pro(root->left, p);(*p)->right = root;(*p) = (*p)->right;(*p)->left = NULL;convertBiNode_pro(root->right, p);}
}struct TreeNode* convertBiNode(struct TreeNode *root) {if (root == NULL) {return root;}struct TreeNode *h = root;while (h->left) { // 找到链表的头h = h->left;}struct TreeNode **p = malloc(sizeof(struct TreeNode*));*p = malloc(sizeof(struct TreeNode));convertBiNode_pro(root, p); // 递归，中序遍历return h;
}