/** * Source : https://oj.leetcode.com/problems/reverse-integer/ * * Created by lverpeng on 2017/7/4. * * Reverse digits of an integer. * * Example1: x =  123, return  321 * Example2: x = -123, return -321 * * * Have you thought about this? * * Here are some good questions to ask before coding. Bonus points for you if you have already thought through this! * * > If the integer's last digit is 0, what should the output be? ie, cases such as 10, 100. * * > Did you notice that the reversed integer might overflow? Assume the input is a 32-bit integer, *   then the reverse of 1000000003 overflows. How should you handle such cases? * * > Throw an exception? Good, but what if throwing an exception is not an option? *   You would then have to re-design the function (ie, add an extra parameter). * */public class ReverseInteger {    /**     * 翻转一个int类型的数，几种特殊情况考虑     * 1. 末尾是零的处理方式：去掉     * 2. 溢出：一种方式注解返回0，一种是当做无符号int输出     *     * 从右至左取出每一位数，然后组成新的数     * 取余，整除的方法     *     * @param num     * @return     */    public int reverse (int num) {        int temp = 0;        int result = 0;        while (num != 0) {            // 判断溢出            if (result > Integer.MAX_VALUE / 10 || result < Integer.MIN_VALUE / 10) {                // 溢出返回0                return 0;            }            // 最后一位数            temp = num % 10;            result = result * 10 + temp;            // 去除最后一位            num = num / 10;        }        return result;    }    /**     * 溢出不返回0，返回翻转后的数，使用long表示     * @param num     * @return     */    public long reverse1 (int num) {        int temp = 0;        long result = 0;        while (num != 0) {            // 最后一位数            temp = num % 10;            result = result * 10 + temp;            // 去除最后一位            num = num / 10;        }        return result;    }    public static void main(String[] args) {        ReverseInteger reverseInteger = new ReverseInteger();        System.out.println(reverseInteger.reverse(123) + " === " + "321");        System.out.println(reverseInteger.reverse(-123) + " === " + "-321");        System.out.println(reverseInteger.reverse(-100) + " === " + "-1");        System.out.println(reverseInteger.reverse(1002) + " === " + "2001");        System.out.println(reverseInteger.reverse(123) + " === " + "321");        System.out.println(reverseInteger.reverse(1463847412) + " === " + "2147483641");        System.out.println(reverseInteger.reverse(2147447412) + " === " + "2147447412");        System.out.println(reverseInteger.reverse(2147447412) + " === " + "2147447412");        // overfow        System.out.println(reverseInteger.reverse(1000000003) + " === " + "0");        System.out.println(reverseInteger.reverse(2147483647) + " === " + "0");        System.out.println(reverseInteger.reverse(-2147483648) + " === " + "0");        System.out.println("");        System.out.println("-------------");        System.out.println("");        //        System.out.println(reverseInteger.reverse1(123) + " === " + "321");        System.out.println(reverseInteger.reverse1(-123) + " === " + "-321");        System.out.println(reverseInteger.reverse1(-100) + " === " + "-1");        System.out.println(reverseInteger.reverse1(1002) + " === " + "2001");        System.out.println(reverseInteger.reverse1(123) + " === " + "321");        //        System.out.println(reverseInteger.reverse1(1463847412) + " === " + "2147483641");        System.out.println(reverseInteger.reverse1(2147447412) + " === " + "2147447412");        System.out.println(reverseInteger.reverse1(2147447412) + " === " + "2147447412");        // overflow        System.out.println(reverseInteger.reverse1(1000000003) + " === " + "3000000001");        System.out.println(reverseInteger.reverse1(2147483647) + " === " + "7463847412");        System.out.println(reverseInteger.reverse1(-2147483648) + " === " + "-8463847412");    }}