HDOJ 1266 Reverse Number（数字反向输出题）

Problem Description
Welcome to 2006’4 computer college programming contest!

Specially, I give my best regards to all freshmen! You are the future of HDU ACM! And now, I must tell you that ACM problems are always not so easy, but, except this one… Ha-Ha!

Give you an integer; your task is to output its reverse number. Here, reverse number is defined as follows:
1. The reverse number of a positive integer ending without 0 is general reverse, for example, reverse (12) = 21;
2. The reverse number of a negative integer is negative, for example, reverse (-12) = -21;
3. The reverse number of an integer ending with 0 is described as example, reverse (1200) = 2100.

Input
Input file contains multiple test cases. There is a positive integer n (n<100) in the first line, which means the number of test cases, and then n 32-bit integers follow.

Output
For each test case, you should output its reverse number, one case per line.

Sample Input
3
12
-12
1200

Sample Output
21
-21
2100

注意：前导0的情况！
例：
输入：
3
-0012560020
00000
00205
输出为：
-2006521
0
502

import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt();
        while (t-- > 0) {
            String str = sc.next();
            int instr = Integer.parseInt(str);
            //System.out.println(instr);
            str = Integer.toString(instr);

            //System.out.println(str);
            if (str.charAt(0) == '-') {
                System.out.print("-");
                int k = 0;
                boolean isOne=false;

                //System.out.println(str.length()+"aaa");

                for (int i = str.length() - 1; i >= 1; i--) {
                    //System.out.println("a:  "+str.charAt(i));
                    if(str.charAt(i)!='0'&&!isOne){
                        //System.out.println("++ "+str.charAt(i));
                        isOne=true;
                    }

                    if (isOne) {
                        System.out.print(str.charAt(i));
                        k++;
                    }
                }
                for (int i = 1; i < str.length() - k; i++) {
                    System.out.print(0);
                }
                System.out.println();
            } else {
                int k = 0;
                boolean isOne=false;
                for (int i = str.length() - 1; i >= 0; i--) {
                    if(str.charAt(i)!='0'&&!isOne){
                        isOne=true;
                    }

                    if (isOne) {
                        System.out.print(str.charAt(i));
                        k++;

                    }
                }

                for (int i = 0; i < str.length() - k; i++) {
                    System.out.print(0);
                }
                System.out.println();

            }

        }
    }

}