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Zero/ZeroLevel/Services/Text/SuffixAutomata.cs

160 lines
4.9 KiB

using System.Collections.Generic;
using System.Linq;
namespace ZeroLevel.Services.Text
{
internal struct state
{
public int len;
public int link;
public Dictionary<char, int> next;
}
public class SuffixAutomata
{
const int MAXLEN = 100000;
private state[] st = new state[MAXLEN * 2];
int sz, last;
public void Init(bool is_reused = false)
{
sz = last = 0;
st[0].len = 0;
st[0].link = -1;
++sz;
// этот код нужен, только если автомат строится много раз для разных строк:
for (int i = 0; i < MAXLEN * 2; ++i)
{
st[i].next = new Dictionary<char, int>();
}
}
public void Extend(char c)
{
int cur = sz++;
st[cur].len = st[last].len + 1;
int p;
for (p = last; p != -1 && !st[p].next.ContainsKey(c); p = st[p].link)
st[p].next[c] = cur;
if (p == -1)
st[cur].link = 0;
else
{
int q = st[p].next[c];
if (st[p].len + 1 == st[q].len)
st[cur].link = q;
else
{
int clone = sz++;
st[clone].len = st[p].len + 1;
st[clone].next = st[q].next;
st[clone].link = st[q].link;
for (; p != -1 && st[p].next.ContainsKey(c) && st[p].next[c] == q; p = st[p].link)
st[p].next[c] = clone;
st[q].link = st[cur].link = clone;
}
}
last = cur;
}
public bool IsSubstring(string w)
{
if (string.IsNullOrEmpty(w)) return true;
bool fail = false;
int n, si = 0;
for (; si < last; si++)
{
if (st[si].next.ContainsKey(w[0]))
{
var start = st[si];
for (int i = 0; i < w.Length; i++)
{
if (start.next.ContainsKey(w[i]) == false)
{
fail = true;
break;
}
n = start.next[w[i]];
start = st[n];
}
break;
}
}
if (si == last)
{
fail = true;
}
return (!fail);
}
public string Intersection(string t)
{
var entries = st.Where(x => x.next.ContainsKey(t[0])).ToArray();
var candidates = entries
.Select(s => Intersection(s, t));
if (candidates != null && candidates.Any())
{
var max = candidates.Max(s => s?.Length ?? 0);
return candidates.FirstOrDefault(c => c != null && c.Length == max);
}
return null;
/*
int v = 0, l = 0, best = 0, bestpos = 0;
for (int i = 0; i < (int)t.Length; ++i)
{
while (v > 0 && !st[v].next.ContainsKey(t[i]))
{
v = st[v].link;
l = st[v].len;
}
if (st[v].next.ContainsKey(t[i]))
{
v = st[v].next[t[i]];
++l;
}
if (l > best)
{
best = l;
bestpos = i;
}
}
var start = bestpos - best + 1;
var length = best;
if (start >= 0 && start < t.Length && (start + length) <= t.Length)
return t.Substring(start, length);
return null;
*/
}
private string Intersection(state entry, string t)
{
int v = 0, l = 0, best = 0, bestpos = 0;
for (int i = 0; i < (int)t.Length; ++i)
{
while (v > 0 && !entry.next.ContainsKey(t[i]))
{
v = entry.link;
l = entry.len;
entry = st[v];
}
if (entry.next.ContainsKey(t[i]))
{
v = entry.next[t[i]];
entry = st[v];
++l;
}
if (l > best)
{
best = l;
bestpos = i;
}
}
var start = bestpos - best + 1;
var length = best;
if (start >= 0 && start < t.Length && (start + length) <= t.Length)
return t.Substring(start, length);
return null;
}
}
}

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