1064. Complete Binary Search Tree (30)

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


没必要建树，直接用一个数组。
代码：

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <map>
using namespace std;
int n,l[1001],tr[2010],c;
void inorder(int k)
{
    if(k > n)return;
    inorder(k * 2);
    tr[k] = l[c ++];
    inorder(k * 2 + 1);
}
void levelprint()
{
    for(int i = 1;i <= n;i ++)
    {
        if(i == 1)printf("%d",tr[i]);
        else printf(" %d",tr[i]);
    }
}
int main()
{
    scanf("%d",&n);
    for(int i = 0;i < n;i ++)
        scanf("%d",&l[i]);
    sort(l,l + n);
    inorder(1);
    levelprint();
}