PAT甲级 -- 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

 

AC：

#include <iostream>
#include <cmath>
using namespace std;

int a, b, sum = 0;
char arr[10];
int index = 0; //字符串标号
int main()
{
    scanf("%d%d", &a, &b);
    sum = a + b;

    if(sum < 0)
    {
        printf("-");
        sum = abs(sum);
    }else if(sum == 0) printf("0");
    while(sum!=0)
    {
        arr[index++] = (sum % 10) + '0';
        sum /= 10;
    }
    for(int i = index-1; i >= 0; i--)
    {
        printf("%c", arr[i]);
        if((i)%3 == 0 && i != 0)
        {
            printf(",");
        }
    }
    return 0;
}

 注意点：

1.注意数字转字符    +‘0’  非-‘0’ ，在这卡了

2. 格式题 一般转化成字符数组/字符串来做