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| # with 2 pointers
def reverseOnlyLetters(S: str) -> str:
n = len(S)
left = 0
right = n - 1
res = list(S)
while right > 0 and not res[right].isalpha():
right -= 1
while left < right:
if res[left].isalpha():
res[left], res[right] = res[right], res[left]
right -= 1
while right > 0 and not res[right].isalpha():
right -= 1
left += 1
return "".join(res)
# a simpler way
def reverseOnlyLetters(S: str) -> str:
stack = [c for c in S if c.isalpha()]
ans = [stack.pop() if c.isalpha() else c for c in S]
return "".join(ans)
assert reverseOnlyLetters("ab-cd") == "dc-ba"
assert reverseOnlyLetters("a-bC-dEf-ghIj") == "j-Ih-gfE-dCba"
assert reverseOnlyLetters("Test1ng-Leet=code-Q!") == "Qedo1ct-eeLg=ntse-T!"
|