一、题目

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?

二、解题思路

1、此题为判断一个数值是否是回文数,即将数值反转后是否等于原数值,如是,则为回文数; 2、先判断数值x是否小于0,如小于0则返回false; 3、再判断x是否等于0,如是,则返回true; 4、如上面两种情况都不符合,则将数值x循环取余取出每一位上的数存入集合中; 5、循环将集合中的数取出,求得反转后的数值; 6、与数值x比较是否相等,如是,则返回true,否则返回false。

三、代码实现

public boolean isPalindrome(int x) {
	if (x < 0) {
		return false;
	} else if (x == 0) {
		return true;
	} else {
		int temp = x;
		int result = 0;
		List<Integer> list = new ArrayList<Integer>();
		
		while (temp != 0) {
			list.add(temp % 10);
			temp = temp / 10;
		}
		
		for (int i = 0; i < list.size(); i++) {
			result = result + list.get(i) * (int)Math.pow(10, list.size() - 1 - i);
		}
		
		if (result == x) {
			return true;
		} else {
			return false;
		}
	}
}