flag6 根据先序和后序序列，创建二叉树

# include <stdio.h>
# include <malloc.h>
typedef struct tree
{
int data;
struct tree* lchild;
struct tree* rchild;
}Tree,*Ptree;
Ptree creattree(int* a,int* b,int astart,int aend,int bstart,int bend);
void travel(Ptree T);
void midtravel(Ptree T);
void main()
{
int firsttravel[5]={6,8,4,7,1};
int lasttravel[5]={8,4,6,1,7};
Ptree T=creattree(firsttravel,lasttravel,0,4,0,4);
travel(T);//先序输出
midtravel(T);//后序输出
}
Ptree creattree(int* a,int* b,int astart,int aend,int bstart,int bend)
{
int i,j,k;
for(i=bstart;i<=bend;i++)
{
if(b[i]==a[astart])
break;
}
Ptree pnew =(Ptree)malloc(sizeof(Tree));
pnew->data=b[i];
//aend=i-1;
j=i-bstart;
k=bend-i;
//bstart=i+1;
printf("astart=%d,aend=%d,i=%d,bstart=%d,bend=%d,j=%d,k=%d\n",astart,aend,i,bstart,bend,j,k);
if(j==0)
pnew->lchild=NULL;
else 
pnew->lchild=creattree(a,b,astart+1,astart+j,bstart,i-1);
if (k==0)
pnew->rchild=NULL;
else pnew->rchild=creattree(a,b,astart+j+1,aend,i+1,bend);
return pnew;


  }
void travel(Ptree T)
{
if(T!=NULL)
{
printf("%d\n",T->data);
}
if(T->lchild!=NULL)
travel(T->lchild);
if(T->rchild!=NULL)
travel(T->rchild);
}
void midtravel(Ptree T)
{
if(T->lchild!=NULL)
midtravel(T->lchild);
if(T!=NULL)
printf("%d\n",T->data);
if(T->rchild!=NULL)
midtravel(T->rchild);
}