1001 A+B Format

1.题目

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 $-10^6\le a,b\le 10^6$. 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.

2.输入输出样例

Sample Input:

-1000000 9

Sample Output:

-999,991

3.题目分析

C语言中int型变量范围在$\pm 2\times 10^9$之间，题目要求相加减的两个数在整型变量所能表示的范围内。题目要求输出格式，从低位起每三位用逗号隔开。因此可考虑转换为字符型变量循环输出。

4.具体代码

#include 
#include 
#include 
using namespace std;

int main(){
	int a, b;
	cin >> a >> b;
	string s = to_string(a + b);//to_string是C++11引入新功能，旧版编译器可能不支持
	int len = s.length();
	for(int i = 0; i < len; i++){
		cout<

5.关于string

在C语言中一般采用 char str[]的字符数组的方式来存放字符串，但C++在STL中加入了string类型，对字符串常用功能进行了封装，更为简便。如要使用string，需添加头文件string，string与string.h是不一样的。