PAT甲级1001 简单A+B特殊输出格式

题目链接：https://pintia.cn/problem-sets/994805342720868352/problems/994805528788582400
想今天秋季或者冬季去考pat甲级，开始刷题了，20分的题还是挺水的，加油吧！奥力给！（其实我懒得写博客，所以直接贴代码记录一下

#include<stdio.h>
#include<string.h>
typedef long long ll;
ll a[100],b[100];
int main()
{
	ll x,y;
	scanf("%lld %lld",&x,&y);
	ll sum=x+y;
	ll ct=0;
	bool flag=0;
	if(sum<0)flag=1,sum=-sum;
	while(sum)
	{
		a[++ct]=sum%10;
		sum/=10;
	}
	for(ll i=ct;i>=1;i--)
	{
		b[ct-i+1]=a[i];
	}
	
	if(ct<=3)printf("%lld\n",x+y);
	else
	{
		if(flag)printf("-");
		ll tmp=ct%3;
		for(ll i=1;i<=tmp;i++)
		{
			printf("%lld",b[i]);
		}
		if(tmp)printf(",");
		for(ll i=tmp+1;i<=ct;i++)
		{
			printf("%lld",b[i]);
			if((i-tmp)%3==0&&i!=ct)printf(",");
		}
		printf("\n");
	}
	scanf("%lld",&x);
}