leetcode——9. Palindrome Number

Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.

Example 1:

Input: 121
Output: true

Example 2:

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

Follow up:

Coud you solve it without converting the integer to a string?

【tips】

1. Originally wanted to use the stack:

    Get the top element of the stack .top(); //This function does not pop the top element of the stack

    Pop: .pop();

2.ArrayList

    Add element: .add(val);

    Get the length of the list: .size();

    Get the element at the i-th position: .get(i);

class Solution {
    public boolean isPalindrome(int x) {
        if(x<0){
            return false;
        }
        if(x==0){
            return true;
        }
        ArrayList list = new ArrayList<Integer>();
        int a;
        boolean flag=true;
        while(x!=0){
            a=x%10;
            list.add(a);
             x=x/10;
        }
        int length=list.size();
        for(int i=0,j=length-1;i<j;i++,j--){
            if(list.get(i)!=list.get(j)){
                flag=false;
            }
        }
        return flag;
        
    }
}