这题也是第二次做，本想第一次做时参考的算法会和老师讲的一样，不想老师讲的算法用在这题感觉还不如思雪园友的算法（http://www.cnblogs.com/sixue/archive/2015/04.html）来的简单，不过老师给的思路是一种挺通用的思路，可以用来解决一系列的问题，但我目前看着有点吃力。我坚持认为对全局变量的使用需十分谨慎，能不用就不用，所以为了不出现全局变量，就无辜多了一串参数。实现代码如下，题目在代码下方
1 #include <stdio.h>
2 #include <stdlib.h>
3
4 int compare(const void * a, const void * b);
5 void inOrder(int * a, int n, int * in, int N);
6
7 int main()
8 {
9 // freopen("in.txt", "r", stdin); // for test
10 int i, N, n;
11 scanf("%d", &N);
12 int a[N];
13 for(i = 0; i < N; i++)
14 {
15 scanf("%d", &n);
16 a[i] = n;
17 }
18
19 qsort(a, N, sizeof(int), compare);
20 int in[N + 1];
21 inOrder(a, 1, in, N);
22 for(i = 1; i <= N; i++)
23 {
24 printf("%d", in[i]);
25 if(i < N)
26 printf(" ");
27 else
28 printf("\n");
29 }
30 // fclose(stdin); // for test
31 return 0;
32 }
33
34 int compare(const void * a, const void * b)
35 {
36 return *(int *)a - *(int *)b;
37 }
38
39 void inOrder(int * a, int n, int * in, int N)
40 {
41 static int i = 0;
42
43 if(n * 2 <= N)
44 inOrder(a, 2 * n, in, N);
45 in[n] = a[i++];
46 if(n * 2 + 1 <= N)
47 inOrder(a, n * 2 + 1, in, N);
48 }
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