Python3 solution, beat 97%
Python\nclass Solution:\n    def modifyString(self, s: str) -> str:\n        chars = \'abcdefghijklmnopqrstuvwxyz\'\n        s_list = list(s)\n        for i in 
```Python\nclass Solution:\n    def modifyString(self, s: str) -> str:\n        chars = \'abcdefghijklmnopqrstuvwxyz\'\n        s_list = list(s)\n        for i in range(len(s)):\n            if s_list[i] != \'?\':\n                continue\n            pre, post = \'\', \'\'\n            if i - 1 >= 0:\n                pre = s_list[i - 1]\n            if i + 1 < len(s):\n                post = s_list[i + 1]\n            print(pre, post)\n            for char in chars:\n                if char != pre and char != post:\n                    s_list[i] = char\n                    break\n        res = \'\'.join(s_list)\n        return res\n```
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