第十一周实践项目~验证算法（2）二叉树构造算法的验证

#include "btree.h"

BTNode *CreateBT1(char *pre,char *in,int n)
//pre存放先序序列,in存放中序序列,n为二叉树结点个数,
//本算法执行后返回构造的二叉链的根结点指针
{
BTNode *s;
char *p;
int k;
if (n<=0) return NULL;
s=(BTNode *)malloc(sizeof(BTNode));
s->data=*pre;
for (p=in; p<in+n; p++)
if (*p==*pre)
break;
k=p-in;
s->lchild=CreateBT1(pre+1,in,k);
s->rchild=CreateBT1(pre+k+1,p+1,n-k-1);
return s;
}

int main()
{
ElemType pre[]="ABDGCEF",in[]="DGBAECF";
BTNode *b1;
b1=CreateBT1(pre,in,7);
printf("b1:");
DispBTNode(b1);
printf("\n");
return 0;
}

#include "btree.h"

BTNode *CreateBT2(char *post,char *in,int n)
//post存放后序序列,in存放中序序列,n为二叉树结点个数,
//本算法执行后返回构造的二叉链的根结点指针
{
BTNode *s;
char r,*p;
int k;
if (n<=0) return NULL;
r=*(post+n-1);                          //根结点值
s=(BTNode *)malloc(sizeof(BTNode));     //创建二叉树结点*s
s->data=r;
for (p=in; p<in+n; p++)                 //在in中查找根结点
if (*p==r)
break;
k=p-in;                                 //k为根结点在in中的下标
s->lchild=CreateBT2(post,in,k);         //递归构造左子树
s->rchild=CreateBT2(post+k,p+1,n-k-1);  //递归构造右子树
return s;
}

int main()
{
ElemType in[]="DGBAECF",post[]="GDBEFCA";
BTNode *b2;
b2=CreateBT2(post,in,7);
printf("b2:");
DispBTNode(b2);
printf("\n");
return 0;
}