exgcd
已知a,b求一组正整数解x,y使得ax+by=gcd(a,b);
我为什要做这样的水题？因为我很弱
1 #include<iostream> 2 #include<cstdio> 3 #include<cstdlib> 4 #include<string> 5 #include<cstring> 6 #include<algorithm> 7 #include<cmath> 8 #include<map> 9 #include<set> 10 using namespace std; 11 typedef long long LL; 12 LL x,y,n,m,l; 13 void exgcd(LL a,LL b,LL &x,LL &y) 14 { 15 if(!b){x=1,y=0;return ;} 16 exgcd(b,a%b,x,y); 17 LL t=x;x=y,y=t-a/b*y; 18 } 19 LL gcd(LL a,LL b) 20 { 21 LL c; 22 while(a%b)c=a%b,a=b,b=c; 23 return b; 24 } 25 int main() 26 { 27 scanf("%lld%lld%lld%lld%lld",&x,&y,&m,&n,&l); 28 LL s,k; 29 LL a=n-m,b=l,c=x-y; 30 LL yue=gcd(a,b); 31 if(c%yue) 32 { 33 printf("Impossible "); 34 return 0; 35 } 36 a/=yue,b/=yue,c/=yue; 37 exgcd(a,b,s,k); 38 s=((c*s)%b+b)%b; 39 if(!s)s+=b; 40 printf("%lld ",s); 41 return 0; 42 }