二叉树按二叉链表形式存储，试编写一个判别二叉树是否是完全二叉树的算法

#include <iostream>
#include <queue>
typedef struct treenode{
    char data;
    struct treenode *left;
    struct treenode *right;
}treenode,*ptreenode;

ptreenode buytreenode(char x)
{
    ptreenode n=(ptreenode) malloc(sizeof (treenode));
    n->data=x;
    n->left= nullptr,n->right= nullptr;
    return n;
}
ptreenode build_tree()//是完全二叉树
{
    ptreenode root= buytreenode('A');
    root->left= buytreenode('B');
    root->right= buytreenode('C');
    root->left->left= buytreenode('D');
    root->left->right= buytreenode('E');
    return root;
}

ptreenode build_tree2()//不是完全二叉树
{
    ptreenode root= buytreenode('A');
    root->left= buytreenode('B');
    root->right= buytreenode('C');
    root->left->left= buytreenode('D');
    root->left->right= buytreenode('E');
    root->left->left->right= buytreenode('F');
    return root;
}
bool iscomplete(ptreenode root)
{
    std::queue<ptreenode> tmp;
    tmp.push(root);
    while(!tmp.empty())
    {
        ptreenode f=tmp.front();
        tmp.pop();
        if(f) tmp.push(f->left),tmp.push(f->right);
        else{
            while(!tmp.empty())
            {
                if(tmp.front()== nullptr) tmp.pop();
                else return false;
            }
        }
    }
    return true;
}
int main() {
    ptreenode root=build_tree();
    ptreenode root2=build_tree2();
    if(iscomplete(root)) printf("It is a completed binary tree\n");
    else printf("NO\n");

    if(iscomplete(root2)) printf("It is a completed binary tree\n");
    else printf("NO\n");
    return 0;
}