問題

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).InputEach 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.OutputFor 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 9Sample Output-999,991

題目地址：https://www.patest.cn/contests/pat-a-PRactise/1001

解答:

#include<stdio.h>
#define LEN 15void FormatPrint(const long int n);int main(){  int a, b;  scanf("%d %d", &a, &b);  FormatPrint(a + b);  return 0;}void FormatPrint(const long int n){  long int num;  if (n == 0) {    putchar('0');    return;  }  else if (n < 0)    num = -n;  else    num = n;  int i = 0;  int tag = 1;  char number[LEN] = { 0 };  while (num > 0) {    number[i++] = '0' + num % 10;    num /= 10;    if (tag % 3 == 0 && num != 0)      number[i++] = ',';    tag++;  }  if (n < 0)    putchar('-');  for (i = i - 1; i >= 0; i--)    putchar(number[i]);}