题目链接:http://poj.org/problem?id=1850 题目大意: 按照字典序对升序排列组成的字母进行编号,给出一个长度不超过10的串,求出它的编号是多少?如果无法进行编号则输出0. 题目分析: 先判断字符串是不是升序的,如果不是升序的则不存在编号,直接输出0即可. 满足升序要求的,则先根据长度len,把长度小于len的串整个处理一下,再对长度为len的递归求解. 1.定义长度为i,以字母c开头的串的个数为f[i][c].很容易看出来:f[i][c]=Σf[i-1][k](k=c…

Code Transmitting and memorizing information is a task that requires different coding systems for the best use of the available space. A well known system is that one where a number is associated to a character sequence. It is considered that the wor…