1064 Complete Binary Search Tree （PAT甲级）

这道题柳婼的解法很巧妙，理解上稍稍抽象，也就是当中序遍历时，level[r] = inorder[t++];

我按照她的思路写的代码如下：

#include 
#include 
#include 

int N, t;
std::vector inorder, level;

void in(int r){
    if(r >= N){
        return;
    }
    in(2 * r + 1);
    level[r] = inorder[t++];
    in(2 * r + 2);
}

int main(){
    scanf("%d", &N);
    inorder.resize(N);
    level.resize(N);
    for(int i = 0; i < N; ++i){
        scanf("%d", &inorder[i]);
    }
    sort(inorder.begin(), inorder.end());
    t = 0;
    in(0);
    for(int i = 0; i < N; ++i){
        printf("%d%s", level[i], i == N - 1 ? "\n" : " ");
    }
    return 0;
}

我一开始的解法如下，复杂很多，先是把loc按levelOrder排列出来，再用中序遍历把loc排列出来，再找loc与值之间一一对应的关系，最后再把值levelOrder列出来。

#include 
#include 
#include 
#include 

题目如下：

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