找出二叉搜索树的最大节点和最小节点

problem:Write recursive versions of TREE-MINIMUM and TREE-MAXIMUM.

typedef struct BiTNode
{
    int data;
    struct BiTNode *lchild, *rchild;      //左右孩子
}BiTNode,*BiTree;

int findmin(BiTree root){  //找出树中最小的节点并返回节点的值
            BiTree ptr = root->lchild;
            int min = 0;
            if(ptr->lchild == null){

             return ptr->data;

      }

         else{

            min = findmin(ptr->lchild);

            return min;

      }

}
int findmax(BiTree root){  //找出树中最大的值并返回其节点的值
            BiTree ptr = root->rchild;
            int max = 0;
            if(ptr->rchild == null){

             return ptr->data;

      }

         else{

            max = findmin(ptr->rchild);

            return max;

      }


}