Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.
Example 1:
Input: 121 Output: true
Example 2:
Input: -121 Output: false Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
Example 3:
Input: 10 Output: false Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
Follow up:
Coud you solve it without converting the integer to a string?
LeetCode:链接
思路来源:LeetCode7:Reverse Integer
1. 负数都不是回文数;2,不能通过将数字转为字符串来判断回文,因为使用了额外的空间(即只能使用空间复杂度 O(1) 的方法);3,注意整数溢出问题。
既然不能将数字转字符串,那仍然可以考虑生成一个反转整数,通过比较反转整数和原整数是否相等来判断回文。
class Solution(object):
def isPalindrome(self, x):
"""
:type x: int
:rtype: bool
"""
if x < 0:
return False
if x == 0:
return True
res = 0
cur = x
while x:
res = res * 10 + x % 10
x = x // 10
return res == cur