程序代码：

#include<stdio.h>
#include<malloc.h>
struct BTnode
{
    char data;
    struct BTnode *Lchild,*Rchild;
};
void CreateBTree(struct BTnode *B)
{

 char ch=getchar();


 if(ch=='a')

 {
        B=NULL;

 }

 else

 {
         B=(struct BTnode *)malloc(sizeof(struct BTnode));

   B->data=ch;

   CreateBTree(B->Lchild);

         CreateBTree(B->Rchild);
}
}

 int Countleaf(struct BTnode *B)

 {
     if(B==NULL) return 0;
     if(B->Lchild==NULL&&B->Rchild==NULL) return 1;
     return(Countleaf(B->Lchild)+Countleaf(B->Rchild));

 }
void main()
{
    struct BTnode B;
CreateBTree(&B);
Countleaf(&B);
}