题解 | #查找两个字符串a,b中的最长公共子串#

import sys

str_1 = input()
str_2 = input()
max_son_str = ""
max_len = 0
if len(str_1) > len(str_2):
    for one_chart_index in range(len(str_2)):
        pp_str = str_1[:]
        while 1:
            son_str = ""
            son_len = 0
            if str_2[one_chart_index] in pp_str:
                char_index = pp_str.index(str_2[one_chart_index])
                son_str += str(str_2[one_chart_index])
                son_len += 1
                pp_str = pp_str.replace(str_2[one_chart_index], "", 1)
            else:
                break
            for pp_index in range(min(len(pp_str)-char_index,len(str_2)-one_chart_index-1)):
                if str_2[one_chart_index + 1 + pp_index] == pp_str[char_index+pp_index]:
                    # 相同子字符串长度数量加1
                    son_str += str(str_2[one_chart_index + 1 + pp_index])
                    son_len += 1
                else:
                    break
            if son_len > max_len:
                max_len = son_len
                max_son_str = son_str
else:
    for one_chart_index in range(len(str_1)):
        pp_str = str_2[:]
        while 1:
            son_str = ""
            son_len = 0
            if str_1[one_chart_index] in pp_str:
                char_index = pp_str.index(str_1[one_chart_index])
                son_str += str(str_1[one_chart_index])
                son_len += 1
                pp_str = pp_str.replace(str_1[one_chart_index], "", 1)
            else:
                break
            for pp_index in range(min(len(pp_str)-char_index,len(str_1)-one_chart_index-1)):
                if str_1[one_chart_index + 1 + pp_index] == pp_str[char_index+pp_index]:
                    # 相同子字符串长度数量加1
                    son_str += str(str_1[one_chart_index + 1 + pp_index])
                    son_len += 1
                else:
                    break
            if son_len > max_len:
                max_len = son_len
                max_son_str = son_str
print(max_son_str)