//SOL
public static BigInteger CalcPermutations(int[,] mat)
{
if (mat[0, 0] == 1 || mat[mat.GetLength(0) - 1, mat.GetLength(1) - 1] == 1)
{
return(0);
}
BigInteger Ways = Unique_Paths.Num_ways(mat.GetLength(0), mat.GetLength(1));
for (int i = 0; i < mat.GetLength(0); i++)
{
for (int j = 0; j < mat.GetLength(1); j++)
{
if (mat[i, j] != 1)
{
continue;
}
bool b1 = (i == 0 || i == mat.GetLength(0) - 1);
bool b2 = (j == 0 || j == mat.GetLength(1) - 1);
if (b2 && b1)
{
Ways -= 1; //IsCorner
}
else if (b1 ^ b2)
{
Ways -= 2; //IsBorder
}
else
{
Ways -= 4; //IsMiddle
}
}
}
return(Ways);
}
public void UniquePathsTests()
{
Unique_Paths obj = new Unique_Paths();
var x = obj.UniquePaths(3, 2); //3
x = obj.UniquePaths(7, 3); //28
x = obj.UniquePaths(1, 1); //1
x = obj.UniquePaths(0, 1); //0
}