二叉树遍历输出

按先序遍历序列创建一个二叉树的二叉链表，并按先序遍历、中序遍历、后序遍历将其输出。
测试用例1node

-+a##*b##c##/d##e##↵

期待输出1ios

前序遍历结果：- + a * b c / d e ↵
中序遍历结果：a + b * c - d / e ↵
后序遍历结果：a b c * + d e / - ↵

#include <iostream>
#include <list>
#include <string>

using namespace std;

struct tree
{
	char data;
	tree* left;
	tree* right;
	tree()
		:left(NULL),right(NULL)
	{}
};

string str;
int curIndex;

void CreateTree(tree* node);
void PreorderOutput(tree* node);
void SequentialOutput(tree* node);
void PostSequenceOutput(tree* node);

int main()
{
	cin >> str;
	tree* root = new tree;
	CreateTree(root);

	cout << "前序遍历结果：";
	PreorderOutput(root);
	cout << endl;

	cout << "中序遍历结果：";
	SequentialOutput(root);
	cout << endl;

	cout << "后序遍历结果：";
	PostSequenceOutput(root);
	cout << endl;

	return 0;
}

void CreateTree(tree* node)
{
	node->data = str[curIndex++];
	if (node->left == NULL && curIndex < str.size())
	{
		if (str[curIndex] == '#')
		{
			curIndex++;
		}
		else
		{
			node->left = new tree;
			CreateTree(node->left);
		}
	}
	if (node->right == NULL && curIndex < str.size())
	{
		if (str[curIndex] == '#')
		{
			curIndex++;
		}
		else
		{
			node->right = new tree;
			CreateTree(node->right);
		}
	}
}

void PreorderOutput(tree* node)
{
	cout << node->data<<" ";
	if (node->left != NULL)
	{
		PreorderOutput(node->left);
	}
	if (node->right != NULL)
	{
		PreorderOutput(node->right);
	}
}

void SequentialOutput(tree* node)
{
	if (node->left != NULL)
	{
		SequentialOutput(node->left);
	}
	cout << node->data << " ";
	if (node->right != NULL)
	{
		SequentialOutput(node->right);
	}
}

void PostSequenceOutput(tree* node)
{
	if (node->left != NULL)
	{
		PostSequenceOutput(node->left);
	}
	if (node->right != NULL)
	{
		PostSequenceOutput(node->right);
	}
	cout << node->data << " ";
}