python数据结构之字符串查找两例

查找字符串中最长连续数字子串

　问题描述

　查找给定字符串中最长的数字字串，返回其起始下标，长度和字串．例如：

　input  ：abc12345cd123ef234567df

　output：15　6　 234567

实现

'''
查找给定字符串中最长的数字字串，返回其起始下标，长度和字串．例如：
input  ：abc12345cd123ef234567df
output：15 6 234567
'''
def find_max_length_str(string):
    str_length = len(string)
    i = 0
    max_length = 0
    num_length = 0
    start_num = 0
    while i < str_length:
        if string[i] > '0' and string[i] < '9':
            start_num = i
            num_length = 0
            while i < str_length and string[i] > '0' and string[i] < '9':
                i += 1
                num_length += 1
            if num_length != 0 and max_length <= num_length:
                max_length = num_length
        i += 1
    return start_num, num_length, string[start_num:start_num + num_length]

　只需遍历一遍字符串，时间复杂度：O(n)

查找数字字符串中最长连续相同数字字串

　问题描述

查找给定数字串中最长连续相同字串，返回其起始下标，长度和子串．例如

input：11233344555666666

output：11 6 666666

　实现

'''
找到数字串中最长连续字串，返回其起始下标，长度和子串
input  ：11233344555666666
output：11 6 666666
'''
def find_same_sequence_num(string):
    str_length = len(string)
    i = 0
    max_length = 0
    start_num = 0
    num_length = 0
    while i < str_length:
        if i + 1 < str_length and string[i] == string[i + 1]:
            start_num = i
            num_length = 1
            while i + 1 < str_length and string[i] == string[i + 1]:
                i += 1
                num_length += 1
            if num_length != 0 and max_length <= num_length:
                max_length = num_length
        i += 1
    return start_num, num_length, string[start_num:start_num + num_length]

同样只需遍历一遍字符串，时间复杂度为O(n)