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valid-palindrome_125.py
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valid-palindrome_125.py
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# A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.
# Given a string s, return true if it is a palindrome, or false otherwise.
# Example 1:
# Input: s = "A man, a plan, a canal: Panama"
# Output: true
# Explanation: "amanaplanacanalpanama" is a palindrome.
# Example 2:
# Input: s = "race a car"
# Output: false
# Explanation: "raceacar" is not a palindrome.
# Example 3:
# Input: s = " "
# Output: true
# Explanation: s is an empty string "" after removing non-alphanumeric characters.
# Since an empty string reads the same forward and backward, it is a palindrome.
# ---------------------------------------Runtime 72 ms Beats 17% Memory 22.4 MB Beats 5.10%---------------------------------------
# My solution 1 "Two pointers"
class Solution:
def isPalindrome(self, s: str) -> bool:
st = "".join(
list(
map(
lambda x: x.lower() if x.isalpha() or x.isalnum() else "",
s,
)
)
)
l, r = 0, len(st) - 1
while l <= r:
if st[l] != st[r]:
return False
l += 1
r -= 1
return True
# My solution 2
# ---------------------------------------Runtime 70 ms Beats 19.51% Memory 22.5 MB Beats 5.10%---------------------------------------
from string import ascii_letters
class Solution:
def isPalindrome(self, s: str) -> bool:
alph = set(ascii_letters + "1234567890")
st = "".join(list(map(lambda x: x.lower() if x in alph else "", s)))
return st == st[::-1]