树的先序,中序,后序遍历的非递归算法

 转自网络

 关键是栈的运用,以此来模拟递归的过程

1.先序遍历非递归算法
#define maxsize 100
typedef struct
{
    Bitree Elem[maxsize];
    int top;
}SqStack;

void PreOrderUnrec(Bitree t)
{
    SqStack s;
    StackInit(s);
    p=t;
   
    while (p!=null || !StackEmpty(s))
    {
        while (p!=null)             //遍历左子树
        {
            visite(p->data);
            push(s,p);
            p=p->lchild;      
        }//endwhile
        
        if (!StackEmpty(s))         //通过下一次循环中的内嵌while实现右子树遍历
        {
            p=pop(s);
            p=p->rchild;        
        }//endif
               
    }//endwhile
   
}//PreOrderUnrec

2.中序遍历非递归算法
#define maxsize 100
typedef struct
{
    Bitree Elem[maxsize];
    int top;
}SqStack;

void InOrderUnrec(Bitree t)
{
    SqStack s;
    StackInit(s);
    p=t;
    while (p!=null || !StackEmpty(s))
    {
        while (p!=null)             //遍历左子树
        {
            push(s,p);
            p=p->lchild;
        }//endwhile
        
        if (!StackEmpty(s))
        {
            p=pop(s);
            visite(p->data);        //访问根结点
            p=p->rchild;            //通过下一次循环实现右子树遍历
        }//endif   
   
    }//endwhile

}//InOrderUnrec


3.后序遍历非递归算法
#define maxsize 100
typedef enum{L,R} tagtype;
typedef struct
{
    Bitree ptr;
    tagtype tag;
}stacknode;

typedef struct
{
    stacknode Elem[maxsize];
    int top;
}SqStack;

void PostOrderUnrec(Bitree t)
{
    SqStack s;
    stacknode x;
    StackInit(s);
    p=t;
   
    do
    {
        while (p!=null)        //遍历左子树
        {
            x.ptr = p;
            x.tag = L;         //标记为左子树
            push(s,x);
            p=p->lchild;
        }
   
        while (!StackEmpty(s) && s.Elem[s.top].tag==R)  
        {
            x = pop(s);
            p = x.ptr;
            visite(p->data);   //tag为R,表示右子树访问完毕,故访问根结点      
        }
        
        if (!StackEmpty(s))
        {
            s.Elem[s.top].tag =R;     //遍历右子树
            p=s.Elem[s.top].ptr->rchild;        
        }   
    }while (!StackEmpty(s));
}//PostOrderUnrec

    原文作者:递归算法
    原文地址: https://blog.csdn.net/youketudou/article/details/6722506
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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