Uva 12347 Binary Search Tree

題目來源：https://uva.onlinejudge.org/external/123/12347.pdf

題意：將輸入的pre_order的Binary tree轉成post_order

做法：直接建議棵樹，再用Postorder(左->右->中)輸出

程式碼：

	#include <iostream>
	#include <cstdio>
	#include <cstdlib>
	using namespace std;
	class Tree
	{
	private:
	struct node
	{
	int value = 0;
	node *left = nullptr;
	node *right = nullptr;
	};
	node* root = nullptr;
	public:
	Tree();
	~Tree();
	void insert(int);
	void Postorder();
	void print_postorder(node*);
	};
	Tree::Tree()
	{
	}
	Tree::~Tree()
	{
	}
	void Tree::insert(int new_node)
	{
	node *tree = new node;
	node *parent = new node;
	tree->value = new_node;
	tree->right = nullptr;
	tree->left = nullptr;
	parent = nullptr;
	if (root == nullptr) {
	root = tree;
	return;
	}
	node* v = root;
	while (v) {
	parent = v;
	if (parent->value > new_node) {
	v = parent->left;
	}
	else {
	v = parent->right;
	}
	}
	if (parent->value > new_node) {
	parent->left = tree;
	}
	else {
	parent->right = tree;
	}
	}
	void Tree::Postorder()
	{
	print_postorder(root);
	}
	void Tree::print_postorder(node *n)
	{
	if (n == nullptr) {
	return;
	}
	print_postorder(n->left);
	print_postorder(n->right);
	printf("%d\n", n->value);
	}
	int main() {
	Tree tree;
	int x;
	while (cin >> x) {
	tree.insert(x);
	}
	tree.Postorder();
	system("PAUSE");
	}

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