欧几里得算法求乘法逆元

扩展的欧几里德算法求乘法逆元

#include

/* 扩展的欧几里德算法求乘法逆元By VC++ 6.0 陈*/

int ExtendedEuclid( int f,int d ,int *result);

int main()

{

int x,y,z;

z = 0;

printf("输入两个数：\n");

scanf("%d%d",&x,&y);

if(ExtendedEuclid(x,y,&z))

printf("%d和%d互素，乘法的逆元是：%d\n",x,y,z);

else

printf("%d和%d不互素，最大公约数为：%d\n",x,y,z);

return 0;

}

int ExtendedEuclid( int f,int d ,int *result)

{

int x1,x2,x3,y1,y2,y3,t1,t2,t3,q;

x1 = y2 = 1;

x2 = y1 = 0;

x3 = ( f>=d )?f:d;

y3 = ( f>=d )?d:f;

while( 1 )

{

if ( y3 == 0 )

{

*result = x3; /* 两个数不互素则result为两个数的最大公约数，此时返回值为零*/ return 0;

}

if ( y3 == 1 )

{

*result = y2; /* 两个数互素则resutl为其乘法逆元，此时返回值为1 */

return 1;

}

q = x3/y3;

t1 = x1 - q*y1;

t2 = x2 - q*y2;

t3 = x3 - q*y3;

x1 = y1;

x2 = y2; x3 = y3; y1 = t1; y2 = t2; y3 = t3; }

}