字符串学习笔记

（⊙ｏ⊙）…也许会咕咕咕……

SAM

#include <bits/stdc++.h>
using namespace std;
int const N = 1e6 * 4;
char s[1000001];
struct SuffixAutomation
{
   int siz, lst, tot;
   long long ans = -1;
   int h[N], size[N];
   struct edge
   {
   	int to, next;
   } e[N];
   struct state
   {
   	int link, len;
   	int next[50];
   } st[N];
   void init()
   {
   	st[siz].len = 0, st[siz].link = -1;
   	lst = 0;
   }
   void add(int u, int v)
   {
   	e[++tot].to = v, e[tot].next = h[u], h[u] = tot;
   }
   void insert(int c)
   {
   	int np = ++siz, p = lst;
   	st[np].len = st[lst].len + 1;
   	size[np] = 1;
   	for (; p != -1 && !st[p].next[c]; p = st[p].link)
   		st[p].next[c] = np;
   	if (p == -1)
   	{
   		st[np].link = 0;
   	}
   	else
   	{
   		int q = st[p].next[c];
   		if (st[q].len == st[p].len + 1)
   		{
   			st[np].link = q;
   		}
   		else
   		{
   			int clone = ++siz;
   			st[clone] = st[q];
   			st[clone].len = st[p].len + 1;
   			st[np].link = st[q].link = clone;
   			while (p != -1 && st[p].next[c] == q)
   			{
   				st[p].next[c] = clone;
   				p = st[p].link;
   			}
   		}
   	}
   	lst = np;
   }
   void prework()
   {
   	for (int i = 1; i <= siz; ++i)
   	{
   		add(st[i].link, i);
   	}
   	dfs(0);
   }
   void dfs(int x)
   {
   	for (int i = h[x]; i; i = e[i].next)
   	{
   		dfs(e[i].to);
   		size[x] += size[e[i].to];
   	}
   	if (size[x] != 1)
   		ans = max((long long)size[x] * st[x].len, ans);
   	return;
   }
} SAM;

int main()
{
   scanf("%s", s);
   int len = strlen(s);
   SAM.init();
   for (int i = 0; i < len; i++)
   {
   	SAM.insert(s[i] - 'a');
   }
   SAM.prework();
   printf("%lld\n", SAM.ans);
   return 0;
}