參考:http://www.cppblog.com/acronix/archive/2010/08/23/124470.aspx?opt=admin
下面是 m^n % k 的快速冪:
// m^n % k
int quickpow(int m,int n,int k)
{
int b = 1;
while (n > 0)
{
if (n & 1) //判斷最後一位(二進制)是否爲1
b = (b*m)%k;
n = n >> 1 ; //右移一位
m = (m*m)%k;
}
return b;
}
當數很大的時候
long long mul(long long a,long long b,long long p)
{
long long res=0;
if (a<b) swap(a,b); //減少循環次數
while (b)
{
if (b&1) res=(res+a)%p;
a=(a<<1)%p;
b>>=1;
}
return res;
}
下面是矩陣快速冪:
Matrix matrixmul(Matrix a,Matrix b) //矩陣乘法
{
int i,j,k;
Matrix c;
for (i = 0 ; i < MAX; i++)
for (j = 0; j < MAX;j++)
{
c.m[i][j] = 0;
for (k = 0; k < MAX; k++)
c.m[i][j] += (a.m[i][k] * b.m[k][j])%9997;
c.m[i][j] %= 9997;
}
return c;
}
Matrix quickpow(Matrix m,long long n)
{
Matrix b = I; //I爲單位矩陣
while (n >= 1)
{
if (n & 1) //按位運算
b = matrixmul(b,m);
n = n >> 1;
m = matrixmul(m,m);
}
return b;
}