Python O(n)
\nclass Solution:\n    def modifyString(self, s: str) -> str:\n        a_to_z = "abcdefghijklmnopqrstuvwxyz"\n        ans = ""\n        for i in range (0,len(s)
```\nclass Solution:\n    def modifyString(self, s: str) -> str:\n        a_to_z = "abcdefghijklmnopqrstuvwxyz"\n        ans = ""\n        for i in range (0,len(s)):\n            if s[i] =="?":\n                left, right ="?","?"\n                if i-1 >=0 :\n                    left = ans[i-1]\n                if i+1< len(s):\n                    right = s[i+1]\n                for newguess in a_to_z:\n                    if newguess != left  and newguess !=right:\n                        ans += newguess\n                        break\n            else:\n                ans += s[i]  \n        return ans\n\t\t\n```
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