04-树6 Complete 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.

  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
  

我的答案：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int b[2048];
int pos = 0;

void sort(int *arr, int num)
{
    int i, j;
    int temp;

    for(i=0;i<num;i++) {
        for(j=i;j<num;j++) {
            if(arr[i]>arr[j]) {
                temp = arr[j];
                arr[j] = arr[i];
                arr[i] = temp;
            }
        }
    }
}

void mid_tree(int root, int N, int a[])
{
    if(root<=N) {
        mid_tree(2*root, N, a);
        b[root] =  a[pos++];
        mid_tree(2*root+1, N, a);
    }
}

int main()
{
    int N, i;
    int data[2048];
    scanf("%d\n", &N);
    for(i=0;i<N;i++) {
        scanf("%d", &data[i]);        
    }
    sort(data, N);
    mid_tree(1, N, data);
    for(i=1;i<=N;i++) {
        if(i==1) {
            printf("%d", b[i]);
        } else {
            printf(" %d", b[i]);
        }
    }

    return 0;
}