Python实现简单查找最长子串功能示例

本文实例讲述了Python实现简单查找最长子串功能。分享给大家供大家参考，具体如下：

题目选自edX公开课 MITx: 6.00.1x Introduction to Computer Science and Programming 课程 Week2 的Problem Set 1的第三题。下面是原题内容。

Assume s is a string of lower case characters.

Write a program that prints the longest substring of s in which the letters occur in alphabetical order. For example, ifs = ‘azcbobobegghakl’, then yo

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ur program should print

Longest substring in alphabetical order is: beggh
In the case of ties, print the first substring. For example, if s = ‘abcbcd’, then your program should print

Longest substring in alphabetical order is: abc
For problems such as these, do not include raw_input statements or define the variable s in any way. Our automated testing will provide a value of s for you – so the code you submit in the following box should assume s is already defined. If you are confused by this instruction, please review L4 Problems 10 and 11 before you begin this problem set.

代码如下：

 # -*- coding:utf-8 -*- #! python2 #判断一个字符串内的字母是否是按字母表顺序 # 如IsStrIncre('abbcdg') 返回 True # IsStrIncre('abbadg') 返回 False # 如果只有一个字符，也返回False def IsStrIncre(s): for cnt in range(len(s) - 1): if len(s) == 1: return False elif s[cnt] > s[cnt+1]: return False return True s = 'abajsiesnwdw'# example code substr = '' for length in range(1, len(s)+1): firstflag = True # a flag to remember the first string that satisfied the requirements # and ignore the strings satisfied the requirements but appeared after for cnt in range(len(s)-length+1): if IsStrIncre(s[cnt: cnt+length]): if firstflag: substr = s[cnt: cnt+length] firstflag = False print 'Longest substring in alphabetical order is: ' + substr 

运行结果：

Longest substring in alphabetical order is: ajs

更多关于Python相关内容感兴趣的读者可查看本站专题：《Python数据结构与算法教程》、《Python列表(list)操作技巧总结》、《Python编码操作技巧总结》、《Python函数使用技巧总结》、《Python字符串操作技巧汇总》及《Python入门与进阶经典教程》

希望本文所述对大家Python程序设计有所帮助。