模m乘法逆元

2019-04-13 14:37发布

long long mod_reverse(long long a,long long m) { long long y=0,x=1,r=a%m,q,t,mm=m; if(r<0)r=r+m; while((m%r)!=0) { a=m;m=r; q=a/m,r=a%m; t=x;x=y-x*q;y=t; } if(r!=1)return 0; if(x<0)x=x+mm; return x; }