Hiho 123 后缀数组四·重复旋律4

首先枚举(k,l)中的这个l，再枚举起始位置i，计算Suffix(i)和Suffix(i+l)的LCP，记作lcp(l, i)，那么k(l, i)就等于lcp(l,i)/l + 1。对于所有的循环节长度l和起始位置i，最大的k(l, i)就是答案。

using System;

namespace Hiho
{
class _123
{
static readonly int MAXN = 1000050;
static char[] ch = new char[MAXN], All = new char[MAXN];
static int[] SA = new int[MAXN], RANK = new int[MAXN], Height = new int[MAXN], tax = new int[MAXN], tp = new int[MAXN], original = new int[MAXN];
static int n, m;
static void RSort()
{
for (int i = 0; i <= m; i++) tax[i] = 0;
for (int i = 1; i <= n; i++) tax[RANK[tp[i]]]++;
for (int i = 1; i <= m; i++) tax[i] += tax[i - 1];
for (int i = n; i >= 1; i--) SA[tax[RANK[tp[i]]]--] = tp[i];
}
static bool cmp(int[] f, int x, int y, int w) { return f[x] == f[y] && f[x + w] == f[y + w]; }
static void Suffix()
{
//SA
for (int i = 1; i <= n; i++)
{
RANK[i] = original[i];
tp[i] = i;
}
m = 2000; RSort();
for (int w = 1, p = 1, i; p < n; w += w, m = p)
{
for (p = 0, i = n - w + 1; i <= n; i++) tp[++p] = i;
for (i = 1; i <= n; i++) if (SA[i] > w) tp[++p] = SA[i] - w;
RSort();
int[] temp = RANK;
RANK = tp;
tp = temp;
RANK[SA[1]] = p = 1;
for (i = 2; i <= n; i++) RANK[SA[i]] = cmp(tp, SA[i], SA[i - 1], w) ? p : ++p;
}
int j, k = 0;
for (int i = 1; i <= n; Height[RANK[i++]] = k)
for (k = k != 0 ? k - 1 : k, j = SA[RANK[i] - 1]; original[i + k] == original[j + k]; ++k) ;
}
static int LCP(int j, int k)
{
if (RANK[j] > RANK[k])
{
int temp = j;
j = k;
k = temp;
}
return (int)ask_min(RANK[j] + 1, RANK[k], 1);
}
//线段树
class Tree
{
public long l, r, add;
public long min;
}
static Tree[] tree = null;

//标记下放们 p == now
static long L(long x)
{
return x << 1;
}
static long R(long x)
{
return x << 1 | 1;
}
static void update(long p)
{
tree[p].min = Math.Min(tree[L(p)].min, tree[R(p)].min);
}

static void spread(long p)
{
if (tree[p].add == 0) return;
tree[L(p)].min += tree[p].add;
tree[R(p)].min += tree[p].add;

tree[L(p)].add += tree[p].add;
tree[R(p)].add += tree[p].add;
tree[p].add = 0;//!!!!!!!
update(p);
return;
}
static void build(long l, long r, long p)
{
if (tree[p] == null) tree[p] = new Tree();
tree[p].l = l;
tree[p].r = r;
if (l == r)
{
tree[p].min = Height[l];
return;
}
long mid = (tree[p].l + tree[p].r) >> 1;
build(l, mid, L(p));
build(mid + 1, r, R(p));
update(p);
return;
}
static long ask_min(long l, long r, long p)
{
if (l <= tree[p].l && tree[p].r <= r)
{
return tree[p].min;
}
spread(p);
long ans = int.MaxValue, mid = (tree[p].l + tree[p].r) >> 1;
if (l <= mid) ans = Math.Min(ans, ask_min(l, r, L(p)));
if (mid < r) ans = Math.Min(ans, ask_min(l, r, R(p)));
update(p);
return ans;
}
static void Main(string[] args)
{
string str = Console.ReadLine();
n = str.Length;
for (int i = 0; i < n; i++) original[i + 1] = str[i];
Suffix();
//segtree
tree = new Tree[4 * (n + 1)];
build(1, n, 1);
//
int ans = 0;
for (int L = 1; L <= n; L++)
{
for (int i = 1; i + L <= n; i += L)
{
int R = LCP(i, i + L);
ans = Math.Max(ans, R / L + 1);
if (i >= L - R % L)
{
ans = Math.Max(LCP(i - L + R % L, i + R % L) / L + 1, ans);
}
}
}
Console.WriteLine(ans);
}
}
}