插入二进制树(非BST）不起作用

在以下代码中，我为二进制树编写了插入功能。但是在每次调用后，它不会将任何节点插入到树上。我已经检查了该算法是否在二进制树上插入。我认为存在一些指针问题，但无法弄清楚为什么会发生这种情况。对于更改指针或用C 中的另一个指针分配的功能是否有任何限制？

//binary tree implementation
#include<iostream>
#include<queue>
using namespace std;
//node class with a constructor 
struct NODE {
    int data;
    NODE *lc,*rc;
    NODE() {
        lc=rc=NULL;
    }
};

//tree class with a constructor
struct TREE {
    NODE *root;
    TREE() {
        root = NULL;
    } 
};

//insertion in a binary tree
//uses queue to keep track of nodes level wise   
void insertNode(NODE *r, int key) {
    NODE *newNode = new NODE;    //getting a new node
    newNode->data = key;         //setting the value of the node to key
    if(!r) {                     //if r is NULL
        //then this is where the new node to be inserted
        r = newNode;
        return;
    }
    queue<NODE*> q;              //Creating a queue of NODE* to store the
    q.push(r);                   //node at each level ,push r to the queue.
    while(!q.empty()) {          //Using a level order traversal
                                //to insert a node to the binary tree.  
        NODE *temp = q.front();  //And inserting the element wherever we
        q.pop();                 //found the node whose left or right child
        if(temp->lc)             //is NULL 
            q.push(temp->lc);    ///If temp has a left child then push it 
        else {                   ///into the queue
                                 ///else insert the node here
            temp->lc = newNode;
            return;
        }
        if(temp->rc)             ///If temp has a right child the push it
            q.push(temp->rc);    ///into the queue
        else {                   ///else insert the node here
             temp->rc = newNode;
             return;
        }
    }
}

//inorder traversal of the tree
void inorder(NODE *r) {
    if(r) {
        inorder(r->lc);
        cout<<r->data<<" ";
        inorder(r->rc);
    }
}

int main() {
    TREE t;
    insertNode(t.root,5);           //inserting 5 to the tree t
    insertNode(t.root,10);          //inserting 10 to the tree t
    insertNode(t.root,15);          //inserting 15 to the tree t
    inorder(t.root);     `          //Now traversing the tree.
                                    ///**But after each insertion root of 
                                    ///tree t is still empty.
                                    ///it means the pointer is not being 
                                    ///changed by the insertionNode fn 
                                    ///but cant figure this out
    return 0;
}