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Re:使用欧拉准则计算勒让德符号,直接计算a^((p-1)/2) 是否为1既可In Reply To:使用欧拉准则计算勒让德符号,直接计算a^((p-1)/2) 是否为1既可 Posted by:majia5 at 2009-07-26 13:10:43 #include <iostream>
using namespace std;
int a,p;
long long mod2(int k)
{
int i;
long long m;
m = a%p;
for(i=0;i<k;i++)
m = (m*m)%p;
return m;
}
int done()
{
int k,q=p/2;
long long m=1;
for(k=0;k<32;k++)
if(((1<<k)&q)>0)
m = m*mod2(k)%p;
if(m==1)
return 1;
else
return -1;
}
int main()
{
int t,tt;
scanf("%d",&tt);
for(t=1;t<=tt;t++)
{
scanf("%d%d",&a,&p);
if(a<0&&(p-3)%4==0)
{
a=-a;
printf("Scenario #%d:\n%d\n\n",t,(-1)*done());
}
else
{
if(a<0&&(p-1)%4==0) a=-a;
printf("Scenario #%d:\n%d\n\n",t,done());
}
}
return 0;
}
...可不可以讲一下他的计算思路。。看不懂啊
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