1099 Build A Binary Search Tree （30 分）

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.

Given the structure of a binary tree and a sequence of distinct integer keys, there is only one way to fill these keys into the tree so that the resulting tree satisfies the definition of a BST. You are supposed to output the level order traversal sequence of that tree. The sample is illustrated by Figure 1 and 2.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (≤100) which is the total number of nodes in the tree. The next N lines each contains the left and the right children of a node in the format left_index right_index, provided that the nodes are numbered from 0 to N−1, and 0 is always the root. If one child is missing, then −1 will represent the NULL child pointer. Finally N distinct integer keys are given in the last line.

Output Specification:

For each test case, print in one line the level order traversal sequence of that tree. All the numbers must be separated by a space, with no extra space at the end of the line.

Sample Input:

9
1 6
2 3
-1 -1
-1 4
5 -1
-1 -1
7 -1
-1 8
-1 -1
73 45 11 58 82 25 67 38 42

Sample Output:

58 25 82 11 38 67 45 73 42

#include<cstdio>
#include<queue>
#include<algorithm>
using namespace std;
const int maxn=110;
struct node{
	int data;
	int lchild,rchild;
}Node[maxn];

int n, in[maxn],num=0; //n为结点个数，in为中序序列，num为已经填入/输出的结点个数
void inOrder(int root){
	if(root==-1){
		return ;
	}
	inOrder(Node[root].lchild);
	Node[root].data=in[num++];     //填入序列中的整数 
	inOrder(Node[root].rchild);
} 
void BFS(int root){
	queue<int> q; //注意队列里是存地址
	q.push(root);
	num=0;
	while(!q.empty()){
		int now=q.front();
		q.pop();
		printf("%d",Node[now].data);
		num++;
		if(num<n)printf(" ");
		if(Node[now].lchild!=-1)q.push(Node[now].lchild); 
		if(Node[now].rchild!=-1)q.push(Node[now].rchild);
	} 
}

int main(){
	int lchild,rchild;
	scanf("%d", &n); //结点数
	for(int i=0;i<n;i++){
		scanf("%d%d",&lchild,&rchild);
		Node[i].lchild=lchild;
		Node[i].rchild=rchild;
	} 
	for(int i=0;i<n;i++){
		scanf("%d",&in[i]);
	} 
	sort(in,in+n);
	inOrder(0);
	BFS(0);
	return 0;
}