Implement binary tree image using a circular Method

The program contains recursive and cyclic methods.

#include <iostream>#include <queue>using namespace std;struct tree{int value;tree *left;tree *right;};tree *create(){int n;cin>>n;if (n == 0){return NULL;}else{tree *root = new tree;root->value = n;root->left = create();root->right = create();return root;}}void pre(tree *root){if (root == NULL){return;}else{cout<<root->value<<" ";pre(root->left);pre(root->right);}}void mirror_digui(tree *root){if (root == NULL || (root->left==NULL && root->right==NULL)){return ;}tree *temp = root->left;root->left = root->right;root->right = temp;if (root->left != NULL){mirror_digui(root->left);}if (root->right != NULL){mirror_digui(root->right);}}void mirror_xunhuan(tree *root){if (root == NULL || (root->left==NULL && root->right==NULL)){return ;}queue<tree *> q;q.push(root);while(!q.empty()){tree *newroot = q.front();q.pop();tree *temp = newroot->left;newroot->left = newroot->right;newroot->right = temp;if (newroot->left!=NULL){q.push(newroot->left);}if (newroot->right!=NULL){q.push(newroot->right);}}}int main(){tree *root = create();pre(root);cout<<endl;mirror_xunhuan(root);pre(root);return 0;}