A1020 Tree Traversals [中序后序建树]

题目大意：给你中序后序，要求输出层序。

#include<iostream>
#include<vector>
#include<queue>
using namespace std;
const int maxn = 50;
struct node
{
	int data;
	node* left, * right;
};
int pre[maxn], in[maxn], post[maxn];
int n;
node* create(int postl, int postr, int inl, int inr)
{
	if (postl > postr)
		return NULL;
	node* root = new node;
	root->data = post[postr];
	int i;
	for (i = inl; i <= inr; i++)
	{
		if (in[i] == post[postr])
			break;
	}
	int numLeft = i - inl;
	root->left = create(postl, postl + numLeft-1, inl, i - 1);
	root->right = create(postl + numLeft, postr - 1, i + 1, inr);
	return root;
}
int num = 0;
void  bfs(node* root)
{
	queue<node*>q;
	q.push(root);
	while (!q.empty())
	{
		node* now = q.front();
		q.pop();
		cout << now->data;
		num++;
		if (num < n) cout << " ";
		if (now->left != NULL) q.push(now->left);
		if (now->right != NULL) q.push(now->right);
	}
}
int main()
{
	node* T;
	cin >> n;
	for (int i = 0; i < n; i++)
		cin >> post[i];
	for (int i = 0; i < n; i++)
		cin >> in[i];
	T = create(0,n-1,0,n-1);
	bfs(T);
	return 0;
}