找出二叉树中序遍历的所求节点的下一个节点

typedef struct node
{
int data;
struct node* left;
struct node* right;
struct node* parent;
}NODE;

NODE *findSuccessorInorder(NODE* node)
{
NODE *pNode = node;

if (pNode->right != NULL)
{
pNode = pNode->right;
while (pNode->left != NULL)
{
pNode = pNode->left;
}

return pNode;
}
else if (pNode->parent)
{
NODE *pParent = pNode->parent;

while (pParent && pParent->right == pNode)
{
pNode = pParent;
pParent = pNode->parent;
}

return pParent;
}
else
{
return NULL;
}
}