leetcode: 9. Palindrome Number

最新推荐文章于 2025-08-13 22:03:49 发布

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本文介绍了一种不使用额外空间判断整数是否为回文数的方法。通过将整数转换为字符串并比较其正反顺序是否一致来实现，同时考虑了负数不能成为回文数的情况。

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Problem

# Determine whether an integer is a palindrome. Do this without extra space.
#
# click to show spoilers.
#
# Some hints:
#
# Could negative integers be palindromes? (ie, -1)
#
# If you are thinking of converting the integer to string, 
# note the restriction of using extra space.
#
# You could also try reversing an integer. 
# However, if you have solved the problem "Reverse Integer", 
# you know that the reversed integer might overflow. How would you handle such case?
#
# There is a more generic way of solving this problem.

AC

class Solution():
    def isPalindrome(self, x):
        if x < 0:
            return False
        l = list(str(x))
        return l == list(reversed(l))


if __name__ == '__main__':
    assert Solution().isPalindrome(1) == True
    assert Solution().isPalindrome(12321) == True
    assert Solution().isPalindrome(12320) == False
    assert Solution().isPalindrome(-12321) == False