已知二叉树前序中序，构造二叉树

BTNode *CreateBT1(char *pre,char *in,int n){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=CreatBT1(pre+1,in,k);s->rchild=CreatBT1(pre+k+1,p+1,n-k-1);return s;}