LeetCode: 9-Palindrome

9. Number of palindrome

Determine whether an integer is a palindrome. The palindrome number refers to the same integer in both positive order (from left to right) and reverse order (from right to left).

Example 1:

Input: 121
Output: true
Example 2:

Input: -121
Output: false
Explanation: Reading from left to right, it is -121. Reading from right to left, it is 121-. Therefore it is not a palindrome.
Example 3:

Input: 10
Output: false
Explanation: Reading from right to left, it is 01. Therefore it is not a palindrome.

Problem-solving ideas

Odd number:

even number:

Code

class Solution {
    
    
    public boolean isPalindrome(int x) {
    
    
    //负数直接不是回文
        if(x <0){
    
    
            return false;
        }
        //将数字的每一位存入list
        ArrayList<Integer> list = new ArrayList();

        int temp =0;
        while(x!=0){
    
    
            temp = x%10;
            x = x/10;
            list.add(temp);
        }
        boolean flag =true;
		//将list转成Integer[]
        Integer[] integers = list.toArray(new Integer[list.size()]);
		//遍历，条件的=号是为了解决偶数个的比较问题
        for(int i=0, j=integers.length-1; i<=integers.length/2 && j>=integers.length/2; i++,j--){
    
    
        //判断
            if(integers[i] != integers[j]){
    
    
                flag = false;
            }
        }
        return flag;
    }
}

test