LeetCode-PalindromeNumber

2019-11-14 14:49:53

字體：大中小

供稿：網(wǎng)友

題目：

Determine whether an integer is a palindrome. Do this without extra space.

Some hints:

Could negative integers be palindromes? (ie, -1)

If you are thinking of converting the integer to string, note the restriction of using extra space.

You could also try reversing an integer. However, if you have solved the
There is a more generic way of solving this problem.

思路：

兩種解法，第一種就是reverse它，有溢出也不怕；第二種就是把跟它位數(shù)相同的10的最大次方求出來(lái)，然后同時(shí)除同時(shí)余，對(duì)比兩邊。

package manipulation;public class PalindromeNumber {        public boolean isPalindrome(int x) {        if (x < 0) return false;        int y = x;        int result = 0;        while (y > 0) {                        result = result * 10 + y % 10;                        y = y / 10;        }                return x == result;    }        public boolean isPalindrome2(int x) {        if (x < 0) return false;        int a = 1;        while (x / a >= 10) {            a = a * 10;        }                int left = 0;        int right = 0;        while (x > 0 && a > 1) {            left = x / a;            right = x % 10;            if (left != right) return false;            x = (x % a) / 10;            a = a / 100;        }                return true;    }        public static void main(String[] args) {        // TODO Auto-generated method stub        PalindromeNumber p = new PalindromeNumber();        System.out.println(p.isPalindrome(1234567890));    }}