java_patest甲级真题1001. A+B Format

Calculate a + b and output the sum in standard format -- that is, the digits must be separated into groups of three by commas (unless there are less than four digits).

Input

Each input file contains one test case. Each case contains a pair of integers a and b where -1000000 <= a, b <= 1000000. The numbers are separated by a space.

Output

For each test case, you should output the sum of a and b in one line. The sum must be written in the standard format.

-1000000 9

-999,991

import java.util.*;
public class Main
{
	public static void main(String[] args)
        {
        	Scanner scanner = new Scanner(System.in);
          	int a, b;
          	a = scanner.nextInt();
          	b = scanner.nextInt();
          	int sum;
          	sum = a + b;
          	boolean flag = true;
          	if(sum < 0 )
          	{
          		flag = false;
          		sum = -sum;
          	}
          	String str = ""+sum;
          	StringBuilder sb = new StringBuilder(str);
          	for(int i = sb.length()-3; i>0 ; i = i - 3)
                {
                	sb.insert(i,",");
                }
          	if(flag)
          		System.out.println(sb);
          	else
          		System.out.println("-"+sb);
        }
}

题目分析：

本人选择的是java方面，初学者，不太会用什么来写，本题目要求的 其实就是 A+B 按照格式输出， 自然而然的 我就想到了用String 但是String不可变，也就是无法增加长度，所以我就想到了StringBuilder 真是个好东西，然后 用个循环自然而然就写出来了。 当然也被坑了··没想到还有 负数的情况可能存在一种： -314 他可能会 -，314如果不考虑到这种情况的话，所以 我在循环之前判断一下 然后用一个flag 作为标记，这样子 就完美解决了。