PAT A1001 A+B Format

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 −. 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

题目大意：给定两个数，计算两个数的和并且按照xxx,xxx,xxx这样的格式输出。
解题思路：
    （1）计算两数之和。
    （2）和是负数就输出一个符号并将和取绝对值，然后将和按位存入int类型数组中。
    （3）从高位到低位输出数组中的数据，每隔三位输出一个逗号。
需要注意的点是：和为0的情况不能忽略，还有就是输出注意最后一位不输出逗号。

#include<iostream>

using namespace std;
int main() {

    int a, b;
    cin >> a >> b;
    int sum = a + b;
    if (sum < 0) { 
        printf("-");
        sum = -sum;
    }
    int res[7];
    int len = 0;//记录长度
    //和为0的情况
    if (sum == 0) res[len++] = 0;
    while (sum) {
        //将sum按位存储，从低位到高位
        res[len++] = sum % 10;
        sum = sum / 10;
    }
    //输出时从高位到低位输出
    for (int i = len - 1; i >= 0; i--) {
        printf("%d", res[i]);
        //每三位输出一个逗号，最后一位除外
        if (i > 0 && i % 3 == 0) printf(",");
    }
    cout << endl;
    system("pause");
    return 0;
}