1099 Build A Binary Search Tree

                     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 <iostream>
#include<bits/stdc++.h>
using namespace std;
int n;
struct Node
{
    int val,l,r;
}node[101];
int a[101],id=0;
void in(int root)
{
    if(root==-1)
        return;
    in(node[root].l);
    node[root].val=a[id++];
    in(node[root].r);
}
vector<int> ans;
void level(int root)
{
    queue<int> q;
    q.push(root);
    while(q.size()!=0)
    {
        int front=q.front();
        ans.push_back(node[front].val);
        q.pop();
        if(node[front].l!=-1)
            q.push(node[front].l);
        if(node[front].r!=-1)
            q.push(node[front].r);
    }
}
int main()
{
    cin>>n;
    for(int i=0;i<n;i++)
    {
        cin>>node[i].l>>node[i].r;
    }
    for(int i=0;i<n;i++)
        cin>>a[i];
    sort(a,a+n);
    in(0);
    level(0);
    cout<<ans[0];
    for(int i=1;i<ans.size();i++)
        cout<<" "<<ans[i];
    cout<<endl;
    return 0;
}