Submission #1028768

#	Time	Username	Problem	Language	Result	Execution time	Memory
1028768		isaachew	Portal (BOI24_portal)	C++17	100 / 100	22 ms	1884 KiB

Main

#include <bits/stdc++.h>
/*
 Have a tiling that can be translated by any amount
 */
long long gcd(long long a,long long b){
    while(a!=0&&b!=0){
        a%=b;
        std::swap(a,b);
    }
    return a+b;
}
std::pair<int,int> getmuls(int a,int b){//extended Euclidean algorithm
    int aina=1,ainb=0,bina=0,binb=1;
    while(a!=0&&b!=0){
        int adb=a/b;
        aina-=adb*ainb;
        bina-=adb*binb;
        a=a%b;
        if(a==0)break;
        int bda=b/a;
        ainb-=bda*aina;
        binb-=bda*bina;
        b=b%a;
    }
    return {aina+ainb,bina+binb};
}
int main(){
    std::ios::sync_with_stdio(0);
    std::cin.tie(0);
    int n;
    std::cin>>n;
    long long ia,ib;
    std::cin>>ia>>ib;
    long long xrep=0,yrep=0,yoff=0;
    for(int i=1;i<n;i++){
        long long a,b;
        std::cin>>a>>b;
        a-=ia,b-=ib;
        if(b==0&&yrep==0){//division by 0
            xrep=gcd(a,xrep);
        }else{
            std::pair<int,int> nums=getmuls(b,yrep);
            long long ngcd=nums.first*b+nums.second*yrep;
            long long nxrep=std::abs((a*yrep-yoff*b)/ngcd);
            xrep=gcd(xrep,nxrep);
            yoff=nums.first*a+nums.second*yoff;
            yrep=ngcd;
            if(xrep!=0)yoff%=xrep;
        }
    }
    long long result=std::abs(xrep*yrep);
    std::cout<<(result==0?-1:result)<<'\n';
}

• Subtask 1: 1 / 1
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 29 / 29
• Subtask 5: 15 / 15
• Subtask 6: 35 / 35