【Python】 回文数的四种解法

回文数就是指整数倒过来和原整数相等。

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Example 1:    Input: 121 Output: true

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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.

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Example 3:    Input: 10 Output: false Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

1：整数转字符串，通过下标对比确定该整数是否为回文数

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str_x = str(x) for i in range(0,int(len(str_x)/2)):   if str_x[i] != str_x[-i-1]:     return False return True

2：字符串切片操作，str[index:index:step]，中括号里面分别为：字符起点、终点和步长

1 2	str_x = str(x) return str_x == str_x[::-1]

3：数学计算的方法，对比反转整数的值

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if x<0:   return False temp_x = x; palindromeNum = 0 while temp_x != 0:   palindromeNum = palindromeNum*10 + temp_x%10   temp_x /= 10 return palindromeNum == x

4：整数转字符串，反转字符串，对比反转后字符串与原字符串是否相等

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str_x = str(x) str_y = "" for i in str_x:   str_y = i + str_y return str_y == str_x