Ritual Algorithm Mathematics - Palindromic Numbers

Table of contents

Palindrome

answer:

code:

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Palindrome

9. Palindrome - LeetCode

Given an integer x, return true if x is a palindromic integer; otherwise, return false.

A palindromic number is an integer that reads the same in forward order (from left to right) and in reverse order (from right to left).

For example, 121 is a palindrome, but 123 is not.
 

Example 1:

Input: x = 121
Output: true
Example 2:

Input: x = -121
Output: false
Explanation: Read from left to right, it is -121. Read from right to left, it is 121-. Therefore it is not a palindromic number.
Example 3:

Input: x = 10
Output: false
Explanation: Read from right to left, it is 01. Therefore it is not a palindromic number.
 

hint:

-231 <= x <= 231 - 1

answer:

1. Negative numbers must not be palindrome numbers, return false
2. A positive number calculates its reversed value, and compares whether it is equal to the original value
3. If it is a palindrome, it is equal to return true, if it is not, it is not equal to false

code:

class Solution {
    public boolean isPalindrome(int x) {
        //排除负数
        if(x < 0)
            return false;
        int res = 0;//记录倒叙结果
        int num = x;//等于所给整数
        //赋值
        while(num != 0) {
            res = res * 10 + num % 10;
            num /= 10;
        }
        //判断
        if(res == x){
            return true;
        }else{
            return false;
        }     
    }
}