二叉树三种非递归遍历算法



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