PAT (Advanced Level) Practice —1001 A+B Format （20 分）

题目链接：https://pintia.cn/problem-sets/994805342720868352/problems/994805528788582400

 

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

我怀疑自己是不是脑子是不是有问题...

：题意 求两个数字相加的和并按格式输出和，格式规定，每隔3个数字要有一个 ',' 当然是从后往前啊 10,000 。开始我竟然写成了 cnt++，如果cnt==3，就输出逗号并且cnt再次初始化为0.....真的太蠢了!

：思路

• 将求出的和转化为字符串形式；
• index处理负数的情况；
• 判断剩下的数（len-1-i）是否是3的倍数，如果是，输出逗号，当然除了已到达字符末尾的情况不用输出逗号。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int main(){
	int a,b;
	while(cin>>a>>b){
		int sum=a+b;
		char s[20];
		sprintf(s,"%d",sum);
		int len=strlen(s);
		int index=0;
		if(sum<0){
			cout<<'-';
			index=1;
		}
		int cnt=0;
		for(int i=index;i<=len-1;i++){
			cout<<s[i];
			int left=len-1-i;
			if(left%3==0&&i!=len-1){
				cout<<',';
			}
		}
		cout<<endl;
	}
	return 0;
}