PAT (Advanced Level) Practice 1001 A+B Format （20 分）（C++）（甲级）

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1001 A+B Format （20 分）

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≤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

#include <cstdio>
#include <cstring>
#include <cmath>

int main()
{
	int a = 0, b = 0;
	scanf("%d %d", &a, &b);
	int sum = a + b;
	int S[5] = { 0 };//辅助栈
	int top = -1;//栈顶指针
	if (!sum) { printf("0"); return 0; }//和为0直接输出了
	if (sum < 0) { printf("-"); sum = -sum; }//和为负数先输出符号，之后正负格式统一
	while (sum)
	{
		S[++top] = sum % 1000;
		sum /= 1000;
	}
	printf("%d", S[top--]);//第一个逗号之前不需要补零
	while (top >= 0) printf(",%03d", S[top--]);//注意输出格式
	return 0;
}