标准序: 短在前,长在后,等长的依次比字
母, 如to < up < cap < cat < too < two <
boat < boot < card
字典序: 依次比字母, 如boat < boot <
cap < card < cat < to < too< two < up
标准序: 短在前,长在后,等长的依次比字
母, 如to < up < cap < cat < too < two <
boat < boot < card
字典序: 依次比字母, 如boat < boot <
cap < card < cat < to < too< two < up