PAT 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 −106≤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

思路

 将a和b相加，按照格式输出。-123456输出为-123，456；-1234567输出为-1，234，567

先计算出位数，将数字转换为字符串，根据位数计算逗号的位置即可。

代码

#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
int main(){
    int a,b;
    cin>>a>>b;
    int c = a+b;
    if(c<0)
    {
        cout<<'-';
        c=-c;
    }
    int x=c;
    int n=0;// 位数
    if(c==0) n++;
    while(x!=0){
        x/=10;
        n++;
    }
    char s[n];
    sprintf(s, "%d", c); 
    for(int i=0;i<n;i++){
        cout<<s[i];
        if((n - i - 1)%3==0&&i!=n-1) cout<<',';
    }
    return 0;
}