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.

If we swap the left and right subtrees of every node, then the resulting tree is called the Mirror Image of a BST.

Now given a sequence of integer keys, you are supposed to tell if it is the preorder traversal sequence of a BST or the mirror image of a BST.

Input Specification:

Each input file contains one test case. For each case, the first line contains a positive integer N (≤1000). Then N integer keys are given in the next line. All the numbers in a line are separated by a space.

Output Specification:

For each test case, first print in a line YES if the sequence is the preorder traversal sequence of a BST or the mirror image of a BST, or NO if not. Then if the answer is YES, print in the next line the postorder traversal sequence of that 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 1:

7
8 6 5 7 10 8 11

Sample Output 1:

YES
5 7 6 8 11 10 8

Sample Input 2:

7

8 10 11 8 6 7 5

Sample Output 2:

YES
11 8 10 7 5 6 8

Sample Input 3:

7
8 6 8 5 10 9 11

Sample Output 3:

NO

分析：

　　1.對輸入的一段序列生成一棵二叉搜尋樹

　　2.判斷：

　　　　　　a.此二叉樹的先序遍歷和輸入的序列相等，則輸出此二叉樹的後序遍歷序列

　　　　　　b.在 a 不成立的情況下，求這棵二叉樹的映象先序遍歷序列，若和輸入的序列相等，則輸出二叉樹的映象後序遍歷序列

　　　　　　c.以上都不成立時，輸出 "NO"

反反覆覆寫完一個小時，除錯用了一個小時半左右。

#include <iostream>
#include<string>
#include<cstdio>
#include<cstring>
#include<vector>
#include<algorithm>
using namespace std;
typedef struct tree
{
    struct tree* rchile;
    struct tree* lchile;
    int key;
}Tree;
vector<int> ori, perorder, minperorder, postorder, minpostorder;
void insert(int num,Tree* &root)
{
    if (root == NULL)
    {
        root = new Tree;
        //Tree* root = (Tree *)malloc(sizeof(tree));
        root->key = num;
        root->lchile = NULL;
        root->rchile = NULL;
        return;
    }
    else
    {
        if (root->key > num)
            insert(num, root->lchile);
        else if (root->key <= num)
            insert(num, root->rchile);
    }
}//建立二叉排序樹
void preorder(Tree* root)
{
    if (root==NULL) return;
    perorder.push_back(root->key);
    preorder(root->lchile);
    preorder(root->rchile);
}//先序遍歷

void minpereorder(Tree* root)
{
    if (root == NULL) return;
    minperorder.push_back(root->key);
    minpereorder(root->rchile);
    minpereorder(root->lchile);
}//映象先序遍歷
void pstorder(Tree* root)
{
    if (root == NULL) return;
    pstorder(root->lchile);
    pstorder(root->rchile);
    postorder.push_back(root->key);
}//後序遍歷
void minptorder(Tree* root)
{
    if (root == NULL) return;
    minptorder(root->rchile);
    minptorder(root->lchile);
    minpostorder.push_back(root->key);
}//映象後序遍歷
int main()
{
    int n;
    Tree* root = NULL;
    cin >> n;
    for (int i = 0; i < n; i++)
    {
        int tem;
        cin >> tem;
        insert(tem,root);
        ori.push_back(tem);        
    }
    /*for (int i = 0; i < ori.size(); i++)
    {
        cout << ori[i] << ' '<<endl;
    }*/
    preorder(root);
    /*for (int i = 0; i < perorder.size(); i++)
    {
        cout << perorder[i] << ' ';
    }*/
    minpereorder(root);
    pstorder(root);
    minptorder(root);

    if (ori == perorder)
    {
        cout << "YES" << endl;
        for (int i = 0; i < postorder.size(); i++)
        {
            int num = 0;
            num++;
            cout << postorder[i];
            if (i != postorder.size() - 1)
                cout << ' ';
        }
    }
    else if (ori == minperorder)
    {
        cout << "YES" << endl;
        for (int i = 0; i < minpostorder.size(); i++)
        {
            int num = 0;
            num++;
            cout << minpostorder[i];
            if (i != minpostorder.size() - 1)
                cout << ' ';
        }
    }
    else
    {
        cout << "NO";
    }
    //system("pause");
    return 0;
}