二叉查找树：删除比指定元素大或小的元素，删除一个范围内的元素；删除、插入、查找非递归以减少运行时间；寻找第i大的元素(Binary Search tree: delete elements larger or smaller than the specified element, delete an element within a range; delete, insert, find function in non recursion to reduce running time; find the ith large element)