9. Palindrome Number【medium】

解题思路：

利用第七题的代码，将数字反转，判断与原数字是否相等即可，这里考虑到负数全部都不是回文数字，所以直接返回false。

实现代码：

// 9. Palindrome Number
int reverse(int x) {
  long result = 0, longX = abs((long)x);
  while (longX > 0) {
    result = result * 10 + longX % 10;
    longX /= 10;
  }
  result = (x > 0) ? result : -result;
  if (result > INT32_MAX || result < INT32_MIN) {
    return 0;
  } else {
    return (int)result;
  }
}
bool isPalindrome(int x) {
  if (x < 0) {
    return false;
  } else {
    return (x == reverse(x));
  }
}

问题描述：

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?