public static Modular Pow(Modular a, int n)
{
switch (n)
{
case 0:
return(1);
case 1:
return(a);
default:
var p = Pow(a, n / 2);
return(p * p * Pow(a, n % 2));
}
}
public Modular dfs(int cur, string last)
{
if (memo[cur].ContainsKey(last))
{
return(memo[cur][last]);
}
if (cur == N)
{
return(1);
}
var ret = new Modular(0);
foreach (char c in ACGT)
{
if (Ok(last + c))
{
ret = ret + dfs(cur + 1, last.Substring(1, 2) + c);
}
}
memo[cur].Add(last, ret);
return(ret);
}
