#include<stdio.h>
#define max 20
struct node* Establishtree();
void preorder(struct node*t);
struct node
{
int data;
struct node*rlink;
struct node*llink;
};
main()
{
struct node*p;
p=Establishtree();
preorder(p);
}
struct node* Establishtree()
{
struct node*n[max];
int i,num,a[max],parent,position,flag,j,k;
do
{
printf("input the num\n");
scanf("%d",&num);
}while(num>max);
for(k=0;k<num;k++)
{
n[k]=(struct node*)malloc(sizeof(struct node));
}
printf("input the root\n");
scanf("%d",&a[0]);
n[0]->data=a[0];
flag=0;
for(k=1;k<num;k++)
{
printf("input the %d num\n",k);
scanf("%d",&a[k]);
n[k]->data=a[k];
n[k]->rlink=NULL;
n[k]->llink=NULL;
printf("input parent\n");
scanf("%d",&parent);
for(i=0;i<k;i++)
{
if(parent==a[i])
{
j=i;
}
}
printf("left or right? left1,right2\n");
scanf("%d",&position);
if(position==1)
{
n[j]->llink=n[k];
n[k]->rlink=NULL;
n[k]->llink=NULL;
}
else
{
n[j]->rlink=n[k];
n[k]->rlink=NULL;
n[k]->llink=NULL;
}
}
return(n[0]);
}
void preorder(struct node*t)
{
struct node*p;
struct node*s[max];
int top;
top=-1;
p=t;
do{
while(p!=NULL)
{
printf("%d\n",p->data);
if(p->rlink!=NULL)
{
top=top+1;
s[top]=p->rlink;
}
p=p->llink;
}
if(top!=-1)
{
p=s[top];
top=top-1;
}
}while((p!=NULL)||(top!=-1));
}
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