PAT甲级1064

最新推荐文章于 2021-05-09 22:51:09 发布

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最新推荐文章于 2021-05-09 22:51:09 发布

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分类专栏： PAT 文章标签： C++ C++程序设计程序设计

本文链接：https://blog.youkuaiyun.com/qq_22194315/article/details/54783989

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1064. Complete Binary Search Tree (30)

时间限制

100 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties:

The left subtree of a node contains only nodes with keys less than the node's key.
The right subtree of a node contains only nodes with keys greater than or equal to the node's key.
Both the left and right subtrees must also be binary search trees.

A Complete Binary Tree (CBT) is a tree that is completely filled, with the possible exception of the bottom level, which is filled from left to right.

Now given a sequence of distinct non-negative integer keys, a unique BST can be constructed if it is required that the tree must also be a CBT. You are supposed to output the level order traversal sequence of this BST.

Input Specification:

Each input file contains one test case. For each case, the first line contains a positive integer N (<=1000). Then N distinct non-negative integer keys are given in the next line. All the numbers in a line are separated by a space and are no greater than 2000.

Output Specification:

For each test case, print in one line the level order traversal sequence of the corresponding complete binary search tree. All the numbers in a line must be separated by a space, and there must be no extra space at the end of the line.

Sample Input:

10
1 2 3 4 5 6 7 8 9 0

Sample Output:

6 3 8 1 5 7 9 0 2 4

#include<cstdio>
#include<algorithm>
#include<vector>
#include<queue>
using namespace std;
struct node
{
	int data;
	node*l, *r;
	node():l(NULL),r(NULL){}
};
void createCBT(node*&root,int N)
{
	queue<node*> Q;
	if (!root)
	{
		root = new node;
		N--;
		if (!N)
			return;
		Q.push(root);
	}
	while (!Q.empty())
	{
		node* t = Q.front();
		Q.pop();
		if (!t->l)
		{
			t->l = new node;
			Q.push(t->l);
			N--;
			if (!N)
				return;
		}
		if (!t->r)
		{
			t->r = new node;
			Q.push(t->r);
			N--;
			if (!N)
				return;
		}
	}
}
vector<int> v; int index = 0;
void inorder(node* &root)
{
	if (!root)
		return;
	inorder(root->l);
	root->data = v[index++];
	inorder(root->r);
}
void levelorder(node*root)
{
	queue<node*> Q;
	if (root)
	{
		printf("%d", root->data);
		Q.push(root);
	}
	while (!Q.empty())
	{
		node*f = Q.front();
		Q.pop();
		if (f->l)
		{
			printf(" %d", f->l->data);
			Q.push(f->l);
		}
		if (f->r)
		{
			printf(" %d", f->r->data);
			Q.push(f->r);
		}
	}
}
int main()
{
	int N;
	scanf("%d", &N);
	node*root = NULL;
	int t;
	for (int i = 0; i <N; i++)
	{
		scanf("%d", &t);
		v.push_back(t);
	}
	createCBT(root, N);//先造出未装填数据的完全二叉树
	sort(v.begin(), v.end());//利用BST的中序遍历是递增序列
	inorder(root);//对完全二叉树进行中序遍历并往其中填数据
	levelorder(root);
	return 0;
}