PTA 7-1 play with binary tree

https://pintia.cn/problem-sets/1259041418971803648/problems/1259046259492220928
（ Title link above ）
The question ：
Given a binary tree in order to traverse and preorder traversal , Please mirror the tree first , And then output the inverted sequence traversal sequence . The so-called mirror reversal , It means to exchange the left and right children of all non leaf nodes .
Use middle order traversal and pre order traversal to build trees ：

node* buildPreInTree(int pl,int pr,int il,int ir){
    
	if(il>ir) return NULL;
	node *root=new node;
	root->num=pre[pl];
	int mid;
	for(int i=il;i<=ir;i++){
    
		if(pre[pl]==in[i]){
    
			mid=i;break;
		}
	}
	int llen=mid-il,rlen=ir-mid;
	root->left=buildPreInTree(pl+1,pl+llen,il,mid-1);
	root->right=buildPreInTree(pl+llen+1,pr,mid+1,ir);
	return root;
}

In this question , To put root->left and root->right transposition , To build trees .
Sequence traversal of binary tree ：

int levelOrderTraverse(node* rt){
    
	queue<node*>q;
	q.push(rt);
	int k=0;
	while(!q.empty()){
    
		node* root=q.front();
		q.pop();
		lev[k++]=root->num;
		if(root->left!=NULL) q.push(root->left);
		if(root->right!=NULL) q.push(root->right);
	}
	return k;
}

Using queues , Considering the output format , Just store it in lev In the array .
AC Code ：

#include <iostream> 
#include <queue>
using namespace std;
int n,pre[35],in[35],lev[35];
struct node{
    
	int num;
	node *left,*right;
};
node* buildPreInTree(int pl,int pr,int il,int ir){
    
	if(il>ir) return NULL;
	node *root=new node;
	root->num=pre[pl];
	int mid;
	for(int i=il;i<=ir;i++){
    
		if(pre[pl]==in[i]){
    
			mid=i;break;
		}
	}
	int llen=mid-il,rlen=ir-mid;
	root->right=buildPreInTree(pl+1,pl+llen,il,mid-1);
	root->left=buildPreInTree(pl+llen+1,pr,mid+1,ir);
	return root;
}
int levelOrderTraverse(node* rt){
    
	queue<node*>q;
	q.push(rt);
	int k=0;
	while(!q.empty()){
    
		node* root=q.front();
		q.pop();
		lev[k++]=root->num;
		if(root->left!=NULL) q.push(root->left);
		if(root->right!=NULL) q.push(root->right);
	}
	return k;
}
int main(){
    
	cin>>n;
	for(int i=0;i<n;i++){
    
		cin>>in[i];
	}
	for(int i=0;i<n;i++){
    
		cin>>pre[i];
	}
	node *rt;
	rt=buildPreInTree(0,n-1,0,n-1);
	int k;
	k=levelOrderTraverse(rt);
	for(int i=0;i<k;i++){
    
		if(i==0) cout<<lev[i];
		else cout<<" "<<lev[i];
	}
	cout<<endl;
	return 0;
}