Title Description:
Given a string S, the "reversed" string is returned, in which characters that are not letters are left in place, and the positions of all letters are reversed.
Example 1:
Input: "ab CD"
Output: "DC Ba"
Example 2:
Enter: "a-bC-dEf-ghIj"
Output: "j-Ih-gfE-dCba"
Example 3:
Type: "test1ng leet = code-q!"
Output: "qedo1ct eelg = nte-t!"
Tips:
S.length <= 100
33 <= S[i].ASCIIcode <= 122
S does not contain \ or“
Solutions:
Traverse the string from both ends to the middle. If both the front and the back are letters, exchange them (since the string cannot be modified, convert the string to a list first). If not, compare the next one.
P.s.33 < = s [i]. ASCII code < = 122 can be directly used to judge whether it is a letter or not
class Solution:
def reverseOnlyLetters(self, S: str) -> str:
begin=0
end=len(S)-1
S=list(S)
while begin<end:
if ((S[begin]>='a' and S[begin]<='z') or (S[begin]>='A' and S[begin]<='Z')) and ((S[end]>='a' and S[end]<='z') or (S[end]>='A' and S[end]<='Z')):#Both the front and back are letters
S[begin],S[end]=S[end],S[begin]
begin+=1
end-=1
elif (S[begin]>='a' and S[begin]<='z') or (S[begin]>='A' and S[begin]<='Z'):#Not followed by letters
end-=1
elif ((S[end]>='a' and S[end]<='z') or (S[end]>='A' and S[end]<='Z')):#It's not preceded by letters
begin+=1
else:
begin+=1
end-=1
return ''.join(S)
Other people's succinct writing of p.s
The. isalpha() method detects whether a string is made up of only letters
class Solution:
def reverseOnlyLetters(self, S: 'str') -> 'str':
S = list(S)
i, j = 0, len(S) - 1
while i < j:
if S[i].isalpha() and S[j].isalpha():
S[i], S[j] = S[j], S[i]
i += 1
j -= 1
if not S[i].isalpha():
i += 1
if not S[j].isalpha():
j -= 1
return "".join(S)