Problem

Given an integer x, return true if x is palindrome integer.
An integer is a palindrome when it reads the same backward as forward. For example, 121 is palindrome while 123 is not.

Example

  1. Input: x = 121
  2. Output: true
  1. Input: x = -121
  2. Output: false
  3. Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
  1. Input: x = 10
  2. Output: false
  3. Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
  1. Input: x = -101
  2. Output: false

Solution

  1. 使用双指针的方式，i从前往后遍历，j从后往前遍历

    1. /**
    2. * @param {number} x
    3. * @return {boolean}
    4. */
    5. var isPalindrome = function (x) {
    6.  if (x < 0) {
    7.      return false;
    8.  }
    10.  const nums = [];
    11.  while(x > 0) {
    12.      nums.push(x % 10);
    13.      x = parseInt(x / 10);
    14.  }
    15.  for (let i = 0, j = nums.length - 1; j > i; j--, i++) {
    16.      if (nums[j] !== nums[i]) {
    17.          return false;
    18.      }
    19.  }
    21.  return true;
    22. };

  2. 只需要判断反转后的数与原数相等，则返回true，否则返回false ```javascript /**

  • @param {number} x

  • @return {boolean} */ var isPalindrome = function (x) { if (x < 0) {

    1.   return false;

    } const oriX = x;

    var revertX = 0;

    while(x > 0) {

      revertX = revertX * 10 + x % 10;
  x = parseInt(x / 10);

    }

    return revertX === oriX; }; ```