code1213 解的个数 扩展欧几里得

#include<iostream>
using namespace std;

int exgcd(int a,int b,int& x,int&y){//扩展欧几里得
if(b==0){
x=1; y=0;
return a;
}
int x2,y2;
int d=exgcd(b,a%b,x2,y2);
x=y2; y=x2-(a/b)*y2;
return d;
}

int main(){
int T; cin>>T;
while(T--){
int a,b,c,lx,hx,ly,hy;
cin>>a>>b>>c>>lx>>hx>>ly>>hy;
c=-c;
if(lx>hx||ly>hy||(a==0&&b==0&&c!=0)){cout<<0<<endl; continue;}
if(a==0||b==0){
long long num_x,num_y;
if(a==0)num_x=hx-lx+1;
else if(c%a==0&&(c/a)<=hx&&(c/a)>=lx)num_x=1;
else num_x=0;
if(b==0)num_y=hy-ly+1;
else if(c%b==0&&(c/b)<=hy&&(c/b)>=ly)num_y=1;
else num_y=0;
cout<<num_x*num_y<<endl;
continue;
}
int x,y;
int d=exgcd(a,b,x,y);
if(c%d!=0){cout<<0<<endl; continue;}
int k=c/d;
x*=k; y*=k;
a/=d; b/=d;
//        cout<<x<<' '<<y<<endl;
if(x<lx){
while(x<lx){
x+=b;
y-=a;
}
}
else{
while(x>=lx){
x-=b;
y+=a;
}
x+=b; y-=a;
}

long long ans=0;
while(x<=hx){
if(y<=hy&&y>=ly){
ans++;
//                cout<<x<<' '<<y<<endl;
}
x+=b;
y-=a;
}
cout<<ans<<endl;
}
}