PAT甲级1001 字符串处理

题目

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≤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

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题解

先上个柳神的题解：

#include
using namespace std;
int main(){
  int a,b;
  cin>> a >> b;
  string c=to_string(a+b);
  int len=c.length();
  for(int i=0;icout<if(c[i]=='-') continue;//这边的单引号尤其要注意，是字符不是字符串
    if((i+1)%3==len%3&&i!=len-1) cout<<",";
  }
  return 0;
}