1043 Is It a Binary Search Tree (25point(s)) Easy only once *二叉排序树

基本点：

题目繁琐无新意；

 

关键点：

左右节点子树交换，可以直接preorder的访问顺序就可以；

 

#include<iostream>
#include<stdlib.h>
#include<stdio.h>
#include<vector> 
#include<string>
#include<math.h>
#include<algorithm>
#include<cstring>
#include<map>
using namespace std;

struct node{
	int data;
	node* lchild;
	node* rchild;
};
node* root =NULL;

vector<int>inseq;
vector<int>preseq;
vector<int>postseq;

void create(node* &root,int n) {
	if (root == NULL) {
		root = new node;
		root->data = n;
		root->lchild = root->rchild = NULL;
		return;
	}
	if (root->data <= n) 
		create(root->rchild, n);
	else
		create(root->lchild, n);
}

void preorder(node* root) {
	if (root == NULL)
		return;
	preseq.push_back(root->data);
	preorder(root->lchild);
	preorder(root->rchild);
}

void postorder(node* root) {
	if (root == NULL)
		return;
	postorder(root->lchild);
	postorder(root->rchild);
	postseq.push_back(root->data);
}

bool charge(vector<int>v1, vector<int>v2) {
	for (int i = 0; i < v1.size(); i++) {
		if (v1[i] != v2[i])
			return false;
	}
	return true;
}

void exchage_tree(node* root) {
	if (root == NULL)
		return;
	exchage_tree(root->lchild);
	exchage_tree(root->rchild);
	node* temp = root->lchild;
	root->lchild = root->rchild;
	root->rchild = temp;
}

int main(){
	int n;
	int a;
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> a;
		create(root,a);
		inseq.push_back(a);
	}
	preorder(root);
	if (charge(preseq, inseq)) {
		//如果相同;
		cout << "YES" << endl;
		postorder(root);
		for (int i = 0; i < postseq.size(); i++) {
			if (i == 0)
				cout << postseq[i];
			else
				cout << " " << postseq[i];
		}
		return 0;
	}
	preseq.resize(0);
	postseq.resize(0);
	exchage_tree(root);
	preorder(root);
	if (charge(preseq, inseq)) {
		//镜像树如果相同;
		cout << "YES" << endl;
		postorder(root);
		for (int i = 0; i < postseq.size(); i++) {
			if (i == 0)
				cout << postseq[i];
			else
				cout << " " << postseq[i];
		}
		return 0;
	}
	cout << "NO";
	return 0;
}