1001 A+B Format (20 分)

1001A+B Format(20分)

Calculatea+band 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 integersaandbwhere−106≤a,b≤106. The numbers are separated by a space.

Output Specification:

For each test case, you should output the sum ofaandbin one line. The sum must be written in the standard format.

Sample Input:

-1000000 9

Sample Output:

-999,991

初始版本：

#include<bits/stdc++.h>
using namespace std;
int main(){
  //freopen("in.txt","r",stdin);
  int a,b,c;
  cin>>a>>b;
  c=a+b;
  char str[100];
  sprintf(str,"%d",c);
  string ans=str;
  char res[100];
  int k=0,count=0;
  for(int i=ans.length()-1;i>=0;i--){
    res[k++]=ans[i];
    count++;
    if(count%3==0&&(i-1>=0)&&(ans[i-1]!='-')) res[k++]=',';
  }
  for(int i=k-1;i>=0;i--){
    cout<<res[i];
  }
  return 0;
}

改进版本

#include<bits/stdc++.h>
using namespace std;
int main() {
    int a, b;
    cin >> a >> b;
    char ans[100];
    sprintf(ans,"%d",a+b);
    int len=strlen(ans); 
    for(int i=0;i<len;i++){
        cout<<ans[i];
        if(ans[i]!='-'&&(i!=len-1)&&(len-i-1)%3==0) cout<<",";//后面剩下3n个数时 要加',' 
    }
    return 0;
}