Description
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 a palindrome while 123 is not.
Example 1:
Input: x = 121
Output: true
Explanation: 121 reads as 121 from left to right and from right to left.
Example 2:
Input: x = -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: x = 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
const isPalindrome = (x) => {
if(x < 0) return false
return x === reversedInteger(x)
}
const reversedInteger = (x)=>{
// declare a temporary container to store the reversed digits from x one by one
const reversed = 0
// truncate the digidts from Ones digit to Hundreds digit of x,
// x needs greater than 0 after each truncate
while(x > 0){
// key point: 'reversed' is the iterator
// the % module function is used to get the number from Ones digit
// 用取模工具依次取个位数，十位数，百位数
reversed = reversed * 10 + x%10
// this is used to remove the Ones digit from the x,
// and x will be a new shorter number and will be used the next time
// 然后 用Math.floor获截取个位数之后的值，直到最后都截取完
x = Math.floor(x/10)
}
return reversed
}