最长子字符串按字母顺序排列

问题描述

编写打印字母以字母顺序出现的s的最长子字符串的程序。例如，如果s ='azcbobobegghakl'，则您的程序应打印

Write a program that prints the longest substring of s in which the letters occur in alphabetical order. For example, if s = 'azcbobobegghakl', then your program should print

按字母顺序的最长子字符串是：beggh

Longest substring in alphabetical order is: beggh

在tie的情况下，打印第一个子字符串。例如，如果s ='abcbcd'，则您的程序应打印

In the case of ties, print the first substring. For example, if s = 'abcbcd', then your program should print

按字母顺序的最长子字符串是：abc

Longest substring in alphabetical order is: abc

推荐答案

在这里，我已经帮助edx学生完成了代码：

Here you go edx student i've been helped to finish the code :

from itertools import count

def long_sub(input_string):
    maxsubstr = input_string[0:0] # empty slice (to accept subclasses of str)
    for start in range(len(input_string)): # O(n)
        for end in count(start + len(maxsubstr) + 1): # O(m)
            substr = input_string[start:end] # O(m)
            if len(substr) != (end - start): # found duplicates or EOS
                break
            if sorted(substr) == list(substr):
                maxsubstr = substr
    return maxsubstr

sub = (long_sub(s))
print "Longest substring in alphabetical order is: %s" %sub

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