public int[] GetPath(Node x)
{
var vs = new SList <int>();
Expose(x);
var stack = new Stack <(Node cur, bool right)>();
stack.Push((x, true));
while (stack.Count > 0)
{
var(cur, right) = stack.Pop();
if (cur == null)
{
continue;
}
if (right)
{
Push(cur);
stack.Push((cur, false));
stack.Push((cur.Right, true));
}
else
{
vs.Add(cur.Index);
stack.Push((cur.Left, true));
}
}
return(vs.ToArray());
}
/// <summary>
/// <para><paramref name="to"/>: 頂点 i からの遷移先。負数は遷移先なしとする。</para>
/// <para><paramref name="start"/>: どの頂点からのパスを見るか</para>
/// <para>制約: <paramref name="to"/>[i] < |<paramref name="to"/>|, 0 ≦ <paramref name="start"/> < |<paramref name="to"/>|</para>
/// <para>計算量: O(N)</para>
/// </summary>
/// <param name="to">数値 i からの遷移先</param>
/// <param name="start">どの頂点からのパスを見るか</param>
public PathLoop(int[] to, int start)
{
var used = new int[to.Length];
var list = new SList <int>(to.Length);
int cur = start;
while (used[cur] == 0)
{
list.Add(cur);
used[cur] = list.Count;
cur = to[cur];
if ((uint)cur >= (uint)to.Length)
{
Straight = list.ToArray();
Loop = Array.Empty <int>();
return;
}
}
var ix = used[cur] - 1;
Straight = list.AsSpan()[..ix].ToArray();
