5_27打卡_树的非递归前中后序遍历

#include<iostream>
#include<queue>
#include<stack>
using namespace std;

typedef struct tree {
	char data;
	tree* lchild;
	tree* rchild;
}tree;


//递归实现创建树
void creatTree(tree*& root)
{
	char ch;
	cin >> ch;
	if (ch == '0')
	{
		root = NULL;
	}
	else {
		root = new tree;
		root->data = ch;
		creatTree(root->lchild);
		creatTree(root->rchild);
	}
}
//树的前中后序 非递归遍历
//前序遍历  根左右
void front_print(tree* root)
{
	stack<tree*> l;
	l.push(root);
	while (!l.empty())
	{
		tree* tmp = l.top();
		cout << tmp->data;
		if (tmp->lchild)
		{
			l.push(tmp->lchild);
		}
		else {
			l.pop();
			if (!l.empty())
			{
				tree* tmp = l.top();
				l.pop();
				if (tmp->rchild)
				{
					l.push(tmp->rchild);
				}
			}
		}
	}
}
//中序遍历 左根右
void mid_print(tree* root)
{
	stack<tree*> l;
	l.push(root);
	while (!l.empty())
	{
		tree* tmp = l.top();
		if (tmp->lchild)
			l.push(tmp->lchild);
		else {
			cout << tmp->data;
			l.pop();
			if (!l.empty())
			{
				tree* tmp = l.top();
				cout << tmp->data;
				l.pop();
				if (tmp->rchild)
				{
					l.push(tmp->rchild);
				}
			}
		}
	}
}

void judgeLeftOrRight(stack<tree*>& l,tree* tmp2)
{
	if (!l.empty())
	{
		if (l.top()->lchild == tmp2)
		{
			l.push(l.top()->rchild);
			return;
		}
		else if (l.top()->rchild == tmp2)
		{
			tree* tmp = l.top();
			l.pop();
			cout << tmp->data;
			judgeLeftOrRight(l, tmp);
		}
	}
}
//后序遍历 左右根
void back_print(tree* root)
{
	stack<tree*> l;
	l.push(root);
	while (!l.empty())
	{
		tree* tmp = l.top();
		if (tmp->lchild)
		{
			l.push(tmp->lchild);
		}
		else
		{
			l.pop();
			cout << tmp->data;
			if (!l.empty())
			{
				judgeLeftOrRight(l, tmp);
			}
		}
	}
}


int main()
{
	//a b d 0 0 e 0 0 c f 0 0 g 0 0
	tree* root;
	creatTree(root);
	print_tree(root);
	cout << endl << "________" << endl;
	front_print(root);
	cout << endl << "_________" << endl;
	mid_print(root);
	cout << endl << "_________" << endl;
	back_print(root);
	return 0;
}