(p138)非递归完成二叉树的遍历

/*
* source.c
*
*  Created on: Feb 25, 2016
*      Author: wing
*/
#include<stdio.h>
#include<stdlib.h>
#define maxsize 1000
struct node{
char n;
struct node *l,*r;
};
struct stack{
struct node **head;
int top;
};
int build(struct node **parent)/*递归建立二叉树*/
{
char n;
scanf("%c",&n);
if (n=='#')
{
*parent=NULL;
return 0;
}
else
{
*parent=(struct node *)malloc(sizeof(struct node));
(*parent)->n=n;
build(&(*parent)->l);
build(&(*parent)->r);
return 0;
}
}
int initstack(struct stack *st)
{
st->head=(struct node**)malloc(sizeof(struct node*)*(maxsize));
st->top=-1;
return 0;
}
int push(struct stack *st,struct node *next)
{
st->head[++(st->top)]=next;
return 0;
}
struct node *pop(struct stack *st)
{
return st->head[st->top--];
}
int pretrav(struct node *root)
{
struct node *next;
struct stack st;
initstack(&st);
next=root;
while (next!=NULL||st.top>=0)
{
if (next!=NULL)
{
printf("%c ",next->n);
push(&st,next);
next=next->l;
}
else
{
next=pop(&st);
next=next->r;
}
}
free(st.head);
return 0;
}
int intrav(struct node *root)
{
struct stack st;
struct node *next;
initstack(&st);
next=root;
while (next!=NULL||st.top>=0)
{
if (next!=NULL)
{
push(&st,next);
next=next->l;
}
else
{
next=pop(&st);
printf("%c ",next->n);
next=next->r;
}
}
free(st.head);
return 0;
}
int postrav(struct node *root)
{
struct node *next,*prev;
struct stack st;
initstack(&st);
next=root;
while (next!=NULL||st.top>=0)
{
while(next!=NULL)
{
push(&st,next);
next=next->l;
}
prev=NULL;
while (st.top>=0)
{
next=st.head[st.top];
if (next->r==prev)
{
printf("%c ",next->n);
prev=pop(&st);
}
else
{
next=next->r;
break;
}
}
if (st.top==-1)
break;
}
return 0;
}
int main(void)
{
struct node **root;
root=(struct node **)malloc(sizeof(struct node*));
build(root);
printf("先序遍历：");
pretrav(*root);
printf("\n中序遍历：");
intrav(*root);
printf("\n后序遍历：");
postrav(*root);
return 0;
}