6_39_二叉树增加两个域不用栈进行递推后序遍历树

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
typedef struct node
{
    int data;
    int mark;
    struct node*lchild,*rchild,*parent;
}tnode,*tree;
tree creat()
{
    int x;
    tree t;
    scanf("%d",&x);
    if(x==0)t=NULL;
    else
    {
        t=(tnode*)malloc(sizeof(tnode));
        t->data=x;
        t->mark=0;
        t->parent=NULL;//初始化它没有双亲
        t->lchild=creat();//左孩子的双亲是它
            if(t->lchild)t->lchild->parent=t;
        t->rchild=creat();//右孩子的双亲是它
            if(t->rchild)t->rchild->parent=t;
    }
    return t;
}
void preorder(tree t)
{
    if(t)
    {
        printf("tree:%d\t",t->data);
        preorder(t->lchild);
        preorder(t->rchild);
    }
}
void postorder(tree t)
{
    while(t)
    {
        if(t->mark==0){//标志为往左子树走
            t->mark=1;//更改标记为往右
            if(t->lchild)t=t->lchild;//如果左子树存在往左走
        }
        else if(t->mark==1){//往右走
            t->mark=2;
            if(t->rchild)t=t->rchild;
        }
        else if(t->mark==2){//访问本节点
            printf("%d\n",t->data);
            t->mark=0;//把它重置，以便下一次遍历
            t=t->parent;//回到双亲
        }
    }
}
int main()
{
    tree t=creat();
    postorder(t);
    postorder(t);
}