已知二叉树后序中序，构造二叉树

BTNode *CreateBT2(char *post,char *in,int n){BTNode *s;char r,*p;int k;if(n<=0)return NULL;r=*(post+n-1);s=(BTNode *)malloc(sizeof(BTNode));s->data=r;for(p=in;p<in+n;p++)if(*p==r)break;k=p-in;s->lchild=CreatBT2(post,in,k);s->rchild=CreatBT2(post+k,p+1,n-k-1);return s;}