/*
*   description:树的遍历示例，非递归版本
*               入栈顺序：
*               前序： 右子树   - 左子树   - 当前节点
*               中序： 右子树   - 当前节点 - 左子树
*               后序： 当前节点 - 右子树   - 左子树
*
*   writeby:    nick
*   date:       2012-10-22 23:56
*/
#include <iostream>
#include <stack>using namespace std;struct node
{int item;bool flag;node *l, *r;node(int n){item=n; l=0; r=0; flag=false;}
};
typedef node *link;//前序遍历
void pretraverse(link h, void visit(link))
{stack<link> s;s.push(h);while(!s.empty()){h = s.top();s.pop();visit( h );if (h->r != 0) s.push(h->r);if (h->l != 0) s.push(h->l);}
}//中序遍历
void midtraverse(link h, void visit(link))
{stack<link> s;s.push(h);while(!s.empty()){h = s.top();s.pop();if(h->flag == true) {visit(h); continue;}if(h->r != 0 && h->r->flag == false) s.push(h->r);if(h->flag==false){ h->flag=true; s.push(h);}if(h->l != 0 && h->l->flag == false) s.push(h->l);}}//后序遍历
void posttraverse(link h, void visit(link))
{stack<link> s;s.push(h);while(!s.empty()){h = s.top();s.pop();if(h->flag == true) {visit(h); continue;}if(h->flag==false){ h->flag=true; s.push(h);}if(h->r != 0 && h->r->flag == false) s.push(h->r);if(h->l != 0 && h->l->flag == false) s.push(h->l);}
}void visit(link p)
{cout << p->item << " ";
}int main()
{link root = new node(4);root->l = new node(5);root->r = new node(6);root->l->l = new node(7);root->l->r = new node(8);cout << "先序遍历：";pretraverse(root, visit);cout << endl << "中序遍历：";midtraverse(root, visit);root->flag          = false;root->l->flag       = false;root->r->flag       = false;root->l->l->flag    = false;root->l->r->flag    = false;cout << endl << "后序遍历：";posttraverse(root, visit);return 0;
}