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  • edX MITx: 6.00.1x Introduction to Computer Science and Programming Using Python 课程 Week 1: Python Basics Problem Set 1 Problem 3

    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, if s = '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

    # Paste your code into this box
    count = 1
    result = s[0]
    while s:
    newcount = 1
    newresult = ''
    i = 0
    while i+1<len(s):
    if ord(s[i]) <= ord(s[i+1]):
    newcount+=1
    newresult+=s[i+1]
    else:
    break
    i+=1
    if newcount>count:
    count = newcount
    result = s[0]+newresult
    s = s[i+1:]
    print(result)

    注:因为只是课程前期,故未使用sort()函数或一些其他高级函数。

    有几点需要注意的地方:

    1)不可去掉 newcount, newresult 变量,因为要找s中的最长子串,故如果后面能找到要替换掉前面稍短的子串

    2)ord(s[i]) <= ord(s[i+1]):     %注意是小于等于号

    3)s = s[i+1:]        %注意i+1:后面不加空格

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  • 原文地址:https://www.cnblogs.com/Bella2017/p/7892493.html
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