LeetCode 1156 需要通过观察找出规律

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思路：本题如果要实现字符串长度增长，只需要考虑两种场景。

  1. aaabaaa，对于b，左和右相等，这时候，总长度是len(left)+len(right)+int(total(a)>current(a))
  2. aaabba，对于a，长度为len(a)+int(total(a)>current(a))

因此，代码如下

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class Solution:
    def maxRepOpt1(self, text: str) -> int:
        grap = [[c,len(list(v))] for c,v in itertools.groupby(text)]
        num = collections.Counter(text)
        res = max(min(k+1,num[c])for c,k in grap)
        for i in range(1,len(grap)):
            if grap[i][1]==1 and i+1 != len(grap) and grap[i-1][0]==grap[i+1][0]:
                res = max(res,min(grap[i-1][1]+grap[i+1][1]+1,num[grap[i-1][0]]))
        return res