浙大PAT甲级 1088

考虑的情况比较多：

（1） 除数为0则，则等号后面输出inf。

（2）求最小公倍数时，两数相乘的范围可能超过了int所表示的范围，因此应选用long long 类型。

AC代码：

#include<iostream>
#include<map>
#include<cstdio>
#include<algorithm>
#include<queue>
#include<cstring>
#include<list>
#include<set>
#include<stack>
#include<cmath>
#include<vector>
#define ll long long
#define inf 999999999
using namespace std;
ll gcd(ll x,ll y)
{
return x%y==0?y:gcd(y,x%y);
}
ll f(ll x,ll y)
{
return x*y/gcd(x,y);
}
void print(ll x,ll y)
{
if(y<0)
{
x=-x;
y=-y;
}
if(x==0)
{
printf("0");
}
else if(x>0)
{
ll r=gcd(x,y);
x/=r;
y/=r;
if(y==1)
{
printf("%lld",x);
return;
}
if(x/y==0)
{
printf("%lld/%lld",x,y);
}
else
{
ll d=x/y;
printf("%lld %lld/%lld",d,x-d*y,y);
}
}
else
{
printf("(-");
x=-x;
ll r=gcd(x,y);
x/=r;
y/=r;
if(y==1)
{
printf("%lld)",x);
return;
}
if(x/y==0)
{
printf("%lld/%lld",x,y);
}
else
{
ll d=x/y;
printf("%lld %lld/%lld",d,x-d*y,y);
}
printf(")");
}
}
int main()
{
string s1;
string s2;
cin>>s1>>s2;
int flag1=0;
if(s1[0]=='-')
{
flag1=1;
s1.erase(0,1);
}
int flag2=0;
if(s2[0]=='-')
{
flag2=1;
s2.erase(0,1);
}
ll mark1;
ll mark2;
ll sum=0;
ll fenzi1;
ll fenmu1;
ll fenzi2;
ll fenmu2;
for(ll i=0;i<s1.size();i++)
{
if(s1[i]=='/')
{
mark1=i;
break;
}
sum*=10;
sum+=s1[i]-'0';
}
fenzi1=flag1==1?-sum:sum;
sum=0;
for(ll i=mark1+1;i<s1.size();i++)
{
sum*=10;
sum+=s1[i]-'0';
}
fenmu1=sum;
if(fenzi1==0)
{
fenmu1=1;
}
sum=0;
for(ll i=0;i<s2.size();i++)
{
if(s2[i]=='/')
{
mark2=i;
break;
}
sum*=10;
sum+=s2[i]-'0';
}
fenzi2=flag2==1?-sum:sum;
sum=0;
for(ll i=mark2+1;i<s2.size();i++)
{
sum*=10;
sum+=s2[i]-'0';
}
fenmu2=sum;
if(fenzi2==0)
{
fenmu2=1;
}
ll fz1=fenzi1;
ll fm1=fenmu1;
ll fz2=fenzi2;
ll fm2=fenmu2;
print(fenzi1,fenmu1);
printf(" + ");
print(fenzi2,fenmu2);
printf(" = ");
ll h=f(fenmu1,fenmu2);
fenzi1=h/fenmu1*fenzi1;
fenzi2=h/fenmu2*fenzi2;
ll fenmu=h;
ll fenzi=fenzi1+fenzi2;
print(fenzi,fenmu);
printf("\n");
fenzi1=fz1;
fenzi2=fz2;
fenmu1=fm1;
fenmu2=fm2;
print(fenzi1,fenmu1);
printf(" - ");
print(fenzi2,fenmu2);
printf(" = ");
h=f(fenmu1,fenmu2);
fenzi1=h/fenmu1*fenzi1;
fenzi2=h/fenmu2*fenzi2;
fenmu=h;
fenzi=fenzi1-fenzi2;
print(fenzi,fenmu);
printf("\n");
fenzi1=fz1;
fenzi2=fz2;
fenmu1=fm1;
fenmu2=fm2;

print(fenzi1,fenmu1);
printf(" * ");
print(fenzi2,fenmu2);
printf(" = ");
fenmu=fenmu1*fenmu2;
fenzi=fenzi1*fenzi2;
print(fenzi,fenmu);
printf("\n");

fenzi1=fz1;
fenzi2=fz2;
fenmu1=fm1;
fenmu2=fm2;
print(fenzi1,fenmu1);
printf(" / ");
print(fenzi2,fenmu2);
printf(" = ");
if(fenzi2==0)
{
printf("Inf\n");
return 0;
}
fenmu=fenmu1*fenzi2;
fenzi=fenzi1*fenmu2;
print(fenzi,fenmu);
printf("\n");

}