擴充套件歐幾里德演算法求乘法逆元(C語言版)
阿新 • • 發佈:2019-01-22
#include <stdio.h>
int ExtendedEuclid( int f,int d ,int *result);
int main()
{
int x,y,z;
z = 0;
printf("輸入兩個數:\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,最大公約數為:%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; /* 兩個數不互素則result為兩個數的最大公約數,此時返回值為零 */
return 0;
}
if ( y3 == 1 )
{
*result = y2; /* 兩個數互素則resutl為其乘法逆元,此時返回值為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;
}
}