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 Specification:

Each input file contains one test case. Each case contains a pair of integers a and b where −10​6​​≤a,b≤10​6​​. The numbers are separated by a space.

Output Specification:

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.

Sample Input:

-1000000 9

Sample Output:

-999,991

題目大意
    計算輸入的A和B的和，按照每三位以','分割的格式輸出
    把a+b的和轉為字串s。除了第一位是負號的情況，只要當前位的下標i滿足(i + 1) % 3 == len % 3並且i不是最後一位，就在逐位輸出的時候在該位輸出後的後面加上一個逗號。

分析

使用python實現就直接相加然後格式化輸出就可以了。

使用java實現，則先判斷相加後是否是負數。是負數先輸出負號。然後倒置字串，每隔三個字元加一個逗號，且如果處於最後的位置則不用新增逗號。最後再翻轉過來，輸出即可。

python實現

if __name__ == "__main__":
    line = input().split(" ")
    a, b = int(line[0]), int(line[1])
    print('{:,}'.format(a+b))

 java實現

import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Main {
	public static void main(String[] args) throws Exception{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] line = br.readLine().split(" ");
		br.close();
		int temp = Integer.valueOf(line[0]) + Integer.valueOf(line[1]);
		if(temp < 0){
			System.out.print("-");
		}
		String s = String.valueOf(Math.abs(temp));
		String a = new StringBuffer(s).reverse().toString();
		String get = "";
		for(int i=0;i<a.length();i++){
			get = get + a.charAt(i);
			if((i+1) %3 == 0 && i != a.length() - 1){
				get = get + ',';
			}
		}
		String out = new StringBuffer(get).reverse().toString();
		System.out.print(out);
	}
}
 

通過這個例子可以看出，如果不想用C/C++來寫PAT的話，python也勉強可以考慮用來解題，但是java真的太慢了