树的遍历【后跟+中跟】

#include<iostream>
#include <algorithm>
#include <cmath>
#include <queue>
using namespace std;
const int N=1e5;
int b[N],a[N];
struct node
{
	int w,l,r;
}tr[N];
int n;
int cnt;
int dfs(int len,int a[],int b[])
{
	if(len<1) return -1;
	if(len == 1) {
		tr[++cnt].w=b[len];
		tr[cnt].l = tr[cnt].r = -1;
		return cnt;
	}
	int res;
	res = ++cnt;
	tr[res].w= b[len];
	int rt=1;
	for(int i=1;i<=len;i++)
		if(a[i]==b[len])
		{
			rt = i;
			break;
		}
	tr[res].l = dfs(rt-1,a,b);
	tr[res].r = dfs(len-rt ,a+rt , b+rt - 1);
	// 后跟序列 去掉左跟的rt-1 个数
	return res;
}

int main()
{
	cin>>n;
	for(int i=1;i<=n;i++) cin>>b[i];
	for(int i=1;i<=n;i++) cin>>a[i];
	int rt = dfs(n,a,b);
	queue<int>q;
	q.push(rt);
	int f=1;
	while(q.size())
	{
		int t=q.front();
		q.pop();
		if(tr[t].l !=-1)
			q.push(tr[t].l);
		if(tr[t].r !=-1)
			q.push(tr[t].r);
		if(f) f=0;
		else cout<<" ";
		cout<<tr[t].w;
	}
	cout<<endl;
	return 0;
}