The process of ordered list unique algorithm is:有序列表唯一化算法的过程是：
AKeep only the first element of each interval of equal elements.只保留每个相等元素区间的第一个元素
BEach time an element is encountered, find backward and delete the same one.每遇到一个元素，向后查找并删除与之雷同者
CEvery time an element is encountered, look ahead and delete the same one.每遇到一个元素，向前查找并删除与之雷同者
DCheck (n ¦ 2) pairs of different elements. For each pair of elements, if they are identical, arbitrarily delete one of them.检查(n¦2)个不同的元素对，对于每一对元素，若雷同则任意删除其一