public bool EquationsPossible(string[] equations)
{
var uf = new UnionFind(26);
foreach (var equation in equations.Where(e => e.Contains("==")))
{
var firstLetter = equation[0];
var fourthLetter = equation[3];
uf.Union(firstLetter - 'a', fourthLetter - 'a');
}
foreach (var equation in equations.Where(e => e.Contains("!=")))
{
var firstLetter = equation[0];
var fourthLetter = equation[3];
if (uf.Connected(firstLetter - 'a', fourthLetter - 'a'))
{
return(false);
}
}
return(true);
}
public void Solve(char[][] board)
{
if (board.Length == 0)
{
return;
}
var m = board.Length;
var n = board[0].Length;
var uf = new UnionFind(m * n + 1);
var dummy = m * n;
for (var i = 0; i < n; ++i)
{
if (board[0][i] == 'O')
{
uf.Union(i, dummy);
}
if (board[m - 1][i] == 'O')
{
uf.Union((m - 1) * n + i, dummy);
}
}
for (var j = 0; j < m; ++j)
{
if (board[j][0] == 'O')
{
uf.Union(j * n, dummy);
}
if (board[j][n - 1] == 'O')
{
uf.Union((j + 1) * n - 1, dummy);
}
}
for (var i = 1; i < n - 1; ++i)
{
for (var j = 1; j < m - 1; ++j)
{
if (board[j][i] == 'O')
{
if (board[j - 1][i] == 'O')
{
uf.Union((j - 1) * n + i, j * n + i);
}
if (board[j + 1][i] == 'O')
{
uf.Union((j + 1) * n + i, j * n + i);
}
if (board[j][i - 1] == 'O')
{
uf.Union(j * n + (i - 1), j * n + i);
}
if (board[j][i + 1] == 'O')
{
uf.Union(j * n + i + 1, j * n + i);
}
}
}
}
for (var i = 1; i < n - 1; ++i)
{
for (var j = 1; j < m - 1; ++j)
{
if (board[j][i] == 'O' && !uf.Connected(j * n + i, dummy))
{
board[j][i] = 'X';
}
}
}
}