leetcode 9. Palindrome Number(python3)

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本文介绍两种判断整数是否为回文数的算法，包括整数反转法和逐位对比法，深入解析算法原理及实现代码。

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9. Palindrome Number

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?

算法1：

将整数反转，比较反转之前和反转之后的值是否一致

class Solution:
def isPalindrome(self, x):
"""
type:x:int
rtype:bool
"""
y=0
tmp=x
if(x<0):
return False
while tmp:
y=y*10+tmp%10
tmp=tmp//10
return y==x

算法2：

从最左边和最右边把整数的数字提取出来

class Solution {
public:
bool isPalindrome(int x)
{
int base=1;
int tmp=x;
if(x<0)
{
return false;
}
while(tmp/10)
{
tmp=tmp/10;

base=base*10;//找出最高位
}
while(x)
{
int left=x/base;
int right=x%10;
if(left!=right)
return false;
x=(x-left*base-right)/10;
base=base/100;
}
return true;
}
};