题目要求：

由a、b、c三个字母组成的任意长度字符串，如果相邻的两个字符是不同的，就用另一个替换，如：

abc->cc或aa

将任意长度的这种字符串进行缩减，直到不能缩减后，最后输出一个整数表示字符串长度。

启初我是使用最简单粗暴的方式

re.sub(r'ab|ba','c',s)
re.sub(r'ac|ca','b',s)
re.sub(r'bc|cb','a',s)

但是这种方式不行，因为这种整体的变换会导致不均匀的减少，比如字符串中的a比较多，但是经过缩减后并没有主动的减少a的数量，反而让b和c减少的更多了。最后本来可以全都消减掉的a全都剩下了。（PS:这是我对这题的理解，但是我感觉其中应该有某种数学规律，可以使用这种数学规律去减少字符，而我使用的方法是一种笨拙的方式完成的。）

def stringReduction(s):
    # select_replace_chr是用于选择替换字符的字典，每个key都对应一个lambda表达式
    select_replace_chr={
        'a_num':lambda s:re.sub(r'bc|cb','a',s,1),
        'b_num':lambda s:re.sub(r'ac|ca','b',s,1),
        'c_num':lambda s:re.sub(r'ab|ba','c',s,1)
    }

#count_num这个字典是用于存储字符串中每个字符的数量
    count_num={
        'a_num':0,
        'b_num':0,
        'c_num':0
    }
    while (True):
        count_num['a_num'] = s.count('a')
        count_num['b_num'] = s.count('b')
        count_num['c_num'] = s.count('c')
#对字典中的元素进行升序排序，再存入字典中。这样第一个元素就是最少的元素。
        count_num=dict(sorted(count_num.items(),key=lambda x:x[1]))
        ss = s
#将前两个较少的字符替换字符串中较多的字符。写两句的原因是"bbca"和'bbac'这种情况。a和c都是最少的元素，如果用a来替换，但字符串的实际情况是"bbac"，程序将不能进行替换，所以我使用了比较笨拙的方式，替换两个较少字符。
#函数的调用已经用颜色分开了，因为我在调用的时候就忘了把参数s添加上了。导致运行时总是提示没有属性。
        s = select_replace_chr[list(count_num.keys())[0]](s)
        s = select_replace_chr[list(count_num.keys())[1]](s)

        if (ss == s):
            break
    print(s)
    return len(s)

这里有一部分测试数据：

babcbbaabcbcbcbaabbccaacccbbbcaaacabbbbaaaccbcccacbbccaccbbaacaccbabcaaaacaccacbaacc
accbaacabbbaacabcbcaccaabcbccbacbcbaabacacababcaacbcccbaccacaabcbaaccbcabccbccbcbbcba
ccaacbabbccbcca
cbcbabccaaaacbbbcccbbb
aaacacaacccbcbacccbacacbaabcc
acabcbbcbabbabcacbaaccb
ccaacaaccabccacabbcbabccbaabacbcccabcaaabaabaccbbaaccacaababbcbacbbcccaccababbccbac
accbacbbcccccaccaababcbccacabbbcbbbcbcbbcaabbbccbaaabbaaaaabcabbcaabacacaaccbbbaccbaacbbcaaba
aaccbccbccabbcc
acccabcccbcaaacbacbcbabbccacb
ccaabacaacccaaaacaaaacacaabbcccaccbbaaabcababcbaacbbbcbabccaacbaccccaabbbbbcaabbcabcacabcccab
aabaaabc
caacbbaabbbbcbbbbbabaccbcaccbcbbabccacc
bbbbaacbcbaaaabaabcaaacbab
acbcbacaacaccbacabbacabcbccacbbaacacaccaccaccacccbabcbcabcabaccbcaacaaabaabcbacacacbcbcbaaabaccaaaac
baccbcabacbbccaabcbaacaaabbacacbbcaacbbcbaaaacaabcabcbbccaacbaaaabaaacacaccabbbaabcacbacabcbbcccb
abcbaaaaccbaccccacbabbbaabaabbbcabababbcbaacaabbaabbcbaaabbbaaabcacacccbaaab
ccbacacabaaaacbaacaacabcaaabbbcacabbbcbaccaacbbcbccbabbabcccbbbaccbbbaccacccbbbabcccaacaa
acbbccccbacacbcaabbcbccbcccaaaabccaabcccbccbacbcaacc
bbabbaccbbcabaccccaccbbcbabbabcbaaccbbcc
bbcbacbacbabcacabbaaccbccacbcccbaccbbbcbacaaaacccaababcacbbcbbacabbccbbcbcbc
accacbabaaacaaabbaaacacbcaccbacc
cccabbbcbaaacaccaccabbacbabbcabcbaacbccbabccbbabacccbbcbbaccbccaacaaccbaabcbccacabcbcbcaaaaccccaccac
ccbaccccbcccccbbccbaabaaabcabaabcbbcbccabccbcbacbcccbaccbabcabbcaa
cccabccbcbbbabbcabcbaccbcbcabcaacaaccaacccbcaac
cbabcacbbbcccaacbcbcabbcaaccbbcaaabcabcbacbaaccbbbabaabbaabbcacaaccaaccbcb
cbcbaaacaabcbbaacaccbcccbabccacccbaabbacbbaabaaacbabaabbacccbbcbabccccbcbbcaaababbbcccbaabacaaaabcc
cbabaabbaccbbaacbcacbabbbbbabacbccaacbcacbcbcbbaabcaabbbababccaccbcaacacbacbbaccaaaabcccb
baccacaaabbbbcbbaacabcbcaccccacbbbbcbccbbaacbcbbbb
abacbbcaaaacbabbbbcbcaccbcbaaaabbccabccccccccbacccacaccbbbcabbcbabbca
babbabcaacabcbaccaaabcbaacaabbbcb
bcabaabbcacaacbacc
bbbabccccccabbaacbcabbcbbcbacabbcabbabbabbaaacaabba
cbbaaaacbbabcaaaccbaacbbbcbcaaccbcabcbbbaaaaabbcacaabcb
bbbcbcbcccbcbcbcaccabaababcbabaccccbbaaaaccccbbababcbcabcaaccbcbbbacababbcabcbb
cabaaccaacccbabccbccbcacaabacabbbcbcabcaccaaabbabbacbbcccacaabbcbbbccbcbccacaccbaabbcabcbbc
acccacbabacaaaabcaacbccaaabbaaba
ccacababbbbcccbcabbaacbcacaccaccabbaacccaabcacacbcca
aaaaacaacaabbbbbaacbcaccbbbabbbcbbabbbcccaabbaacb
abbcbccccabbaabbccabccbbcacccaaacbabbabaaaabbba
bbabbacaabbbcbbcbcbacacbaccaaabbcccacccbbacbcbbbbacbabccaccaabccacaacc
bacaaabcccbbcaabaabbbcbbabcbbbbccaaabccbbbaccbaaaacbcbaaacc
bbcbbabbacccbababcaccbbaacbbccbaaaacbbbcaacbbacaaaabcbbabacacababbabbbbccacbbbbccbaaacabacccaba
abcbabbabbbaaaacbbacbabbabbbaaaabaacccabacaacbabcbaaca
bbbcbbaca
aacc
bcabaaabbaacbccbbbababcacbb
aaccbcbcccaaababcacacaccbcbcacaccccbcabbcccab
caccaaaaacabbaababbccaaacabcbcbbcbaababcbbaaabcaa
accbbbccbbbccbbbcacbcacbbacbbccccbbaababaccaabbbbbcbbcaaaabca
ccabbacbacccaaacbbaaaaaaabaabacabcccabbacacabaccbababcabaccbabcbbbacaaacacccaa
baacccbbaabcacccbbaabaabcabbabaacbcbbb
cbccabbabcabcccbbccabccbcabcaaacccacbbacccbbbbcabcaaccccbbbbcbbcbcacbaabccabaccc
aacacbbbaabbabccbcbbaccccbacbbcbbcbbbbabcbccc
abcbbacaacbcccacbbcbcaaabccaacaabacabbacbcbbabacacaccbbbbabcaccccccbb
bababbbcabccbbaccc
bbcbbcbbc
aababbc
abbcabccccccbbbaabcbaccbabbbbbcbcacabbabacacbacbcaaaacbaccaaaccaabbcabacb
bccbbccbcccabbabbbaacaaacabccacbacabbcabccb
bcbcacbcabaaccaccabaabbbbaaaaccccababaa
bbcbbabbaccabbacbaacacbcbaacbbaacacbabacaccbacbcaccbbbbcbbcaabbbbbcaaccbbbbaccaabc
babbcababcccbbcbbaabcaccabcabcaccbbabcbacbaccaacacaaacabacccacbabaababbbcaaaabcbbabcccaaabaabca
acccaaababcbabaacaabaccaaabbaccbbbacabbbcabbcbcbccabbab
aaabaaaccacccbaccbbcbabbacccacbbacaacbacbcbbbccbbaaccccabbcbabaaabbbcbabccaaca
bbccacbababbbcccbaccaacbaccbccacbbbcaabcacacbcac
ccaaaabcccaaaccbbccbacbcaccaccbbaabaacaacbbaaacbbcabbccbbccacbccbaccabcaccabaaabababbaaacbbbaabc
bbb
bccaaacbaabcacaabaaabcabbcacbbaabcccababbcbacbbbacbbcbbabbcaaccccbbaacccbbccacaabcabbcbbabcbcb
bacabaabbbbbcacbcccabbcccbaaacccacaccaacccaaaabacabbbbbaabbabaacbbbacca
cbac
bacccaabbbbacccbabcccacccabbacabccbcabacacaabababbcbacbccabacbcabacbcbbca
aaccbbcaaabcabcbcacbabcabbbacaacbacccbcccbbcabaacbbacbbbaacabaacacbcccbbaabbabbc
abaccbaabacbaccabbaa
bbccaacbaccbccbcccaaccaccbbabbcacaaaaacbaccabbaccccbbabbaccb
ccbabbabbccbcbacccbbcaabcbbbbcab
cbbbbaabbcbccbbacbcabacabcbcccccbbacbbccabcbccbcabcccccbcbbcbbbccbacaccbaacccabaabccbaba
bcacbaabaaccaaaabcacbacbbccbbaacabcaccbaaabbbbbccacbbbccbc
aacabaabcbaabbccaacaccacbcbbbbacbcabaacabbbacaaaccbccbbcbabacbccbcacbaacbcababbcbacccabbbcccabb
cbbaba
bcbacccaaaccaabbaabccbbbacbbbbbabcabcacaababaaabacbaacabcbc
abbcbcbacbbaaabaaacbcaccacacbaacbccabaccbbacbaacaaccbbccbacaacacccacccccbcbbccaaaca
bccacbaacaacabcabbcccbacacabcabcabcaabccccaabcbcbb
acacaaaccbbccacabbcbabbacbcca
cbaabcacbabbaabaaabbcbcbaaacaaaccaabcbbcc
babaabbbabaacabaacbaabbaaccccccbcabccababbbbcabaccbcbcbbcabccaacacbacabbbcaaccabcccbcaa
accacccbcbccbabaccccbabaaaccaacbabccbcbbaaaca
aabcccabbabaaaaacabcbabccabacbbaacacabbbbb
cbacabbaaacbaccacbbbbcbccaabcbacaaccaacabccbcbccabbcacbababbccabacaaaacaabbcaacbaaaabaccaa
ccbaabbbccacaabaacbccbabaaacababcbcacbbcbabcaccbaaacabbaccbabbcaacaabcacaccac
ccaaaaccbbcccbccbabcaacbcabcbbabbbcccbbcabbacbabbbbabbcbcaab
baabaaaccaaacbbbbcaabbcaababcbabcbcccbcbbcabbbaabbacaaaabacaccccbbcbabaccbbacbccaccababcbaab
aaacabacaabbbccbbbccbaabbcaaacbbacbaccaccbbbcbaaaaccbaaaab
bbcacccabbbbbacaabbbbcbaaccbabacacacccbbacabababacacbcaccaaacaaabacbabbbbbbcab
aababbbbbbcbaabacabbbaccccacccaaccbbaccbaabbbaaaaccbcccccabcabacbbcaacbbca
abbbbbbbbbabaaccacbbacaaaaabaacacbababaccaba
aaaabccbaacabaacbcbacabbabbbcbbabbcbababbcbaaaacacaabcbcbcbbbccabbbccbacbcaccbbcb
a
bbccbbbcbbbcccbaccaabaaccccabaabcabccacabaaabcaabababccabccaacbcaabcbbacbacacbaacabccbaba
cacbaccccabcaaaabcbcacccbbbcabcacbcaccababcaaabcaabbabbcacbcbaabccccccbc

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