/// <summary>
/// <paramref name="x"/>^<paramref name="n"/> mod <paramref name="m"/> を返します。
/// </summary>
/// <remarks>
/// <para>制約: 0≤<paramref name="n"/>, 1≤<paramref name="m"/></para>
/// <para>計算量: O(log<paramref name="n"/>)</para>
/// </remarks>
public static long PowMod(long x, long n, int m)
{
Debug.Assert(0 <= n && 1 <= m);
if (m == 1)
{
return(0);
}
Barrett barrett = new Barrett((uint)m);
uint r = 1, y = (uint)InternalMath.SafeMod(x, m);
while (0 < n)
{
if ((n & 1) != 0)
{
r = barrett.Mul(r, y);
}
y = barrett.Mul(y, y);
n >>= 1;
}
return(r);
}
public static long PowMod(long x, long n, int m)
{
Contract.Assert(0 <= n && 1 <= m, reason: $"0 <= {nameof(n)} && 1 <= {nameof(m)}");
if (m == 1)
{
return(0);
}
Barrett barrett = new Barrett((uint)m);
uint r = 1, y = (uint)InternalMath.SafeMod(x, m);
while (0 < n)
{
if ((n & 1) != 0)
{
r = barrett.Mul(r, y);
}
y = barrett.Mul(y, y);
n >>= 1;
}
return(r);
}
