Python实现简单查找最长子串功能示例_Python

Python实现简单查找最长子串功能示例

2021-06-02 00:24dazuo_01 Python

这篇文章主要介绍了Python实现简单查找最长子串功能,涉及字符串遍历、统计等相关操作技巧,需要的朋友可以参考下

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 your 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