PAT Advanced 1001. A+B Format (20) (C语言实现)

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

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.

Sample Input
-1000000 9
Sample Output
-999,991

思路

两个要点：

两数和为0时要输出0;

注意逗号的输出位置，如不要在数字前面和后面有输出

代码

最新代码@github，欢迎交流 ^_^

#include <stdio.h>
int main()
{
int a, b, sum, count, dec;
scanf("%d%d", &a, &b);
sum = a + b;

if(sum == 0) putchar('0');
if(sum < 0) { putchar('-'); sum = -sum; }

for(count = 0, dec = 1; sum >= dec; count++, dec *= 10) ;

for(int c = count; c; c--, sum %= dec)
{
if(c < count && c % 3 == 0 && c) putchar(',');
putchar('0' + sum / (dec /= 10));
}

return 0;
}