PAT 1001 A+B Format

原题目

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 −10⁶​​ ≤a,b≤10⁶. 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

题目大意

计算a+b的值并按标准格式输出结果。标准格式即：数字需将每三位用逗号(,)分隔开，除非数字的位数小于4位。
输入一对整数a和b，在一行内以标准格式输出a和b的和。

题解

题目过于简单，懒得写注释了。
C语言gcc 6.5.0代码如下：

#include<stdio.h>
#include<math.h>
int main(){
    int a, b;
    scanf("%d %d", &a, &b);
    int sum = a + b;
    if(sum < 0){
        printf("-");
        sum = -sum;
    }
    if(sum >= 1000000){
        printf("%d,", sum/1000000);
        sum -= sum/1000000 * 1000000;
        printf("%03d,", sum/1000);
        sum -= sum/1000 * 1000;
        printf("%03d\n", sum);
    }
    else if(sum >= 1000){
        printf("%d,", sum/1000);
        sum -= sum/1000 * 1000;
        printf("%03d\n", sum);
    }
    else
        printf("%d\n", sum);
    return 0;
}