【刷题】SPOJ 8222 NSUBSTR - Substrings
You are given a string S which consists of 250000 lowercase latin letters at most. We define F(x) as the maximal number of times that some string with length x appears in S. For example for string 'ababa' F(3) will be 2 because there is a string 'aba' that occurs twice. Your task is to output F(i) for every i so that 1<=i<=|S|.
Input
String S consists of at most 250000 lowercase latin letters.
Output
Output |S| lines. On the i-th line output F(i).
Example
Input:
ababa
Output:
3
2
2
1
1
Solution
当 SAM模板题做,建出SAM后,对于一个状态,它的子树size和就是它代表的子串出现次数
然后由于SAM是最简状态自动机,所以有时不一定所有子串都有自己的状态
但是如果一个长度为 \(l\) 的子串出现了 \(k\) 次,那么长度为 \(l-1\) 的子串至少也出现了 \(k\) 次
利用这点,最后再一个循环搞定答案
这里用的基数排序求拓扑序,避免了写dfs,舒服很多
#include<bits/stdc++.h>
#define ui unsigned int
#define ll long long
#define db double
#define ld long double
#define ull unsigned long long
const int MAXN=250000+10;
int las=1,tot=1,size[MAXN<<1],ch[MAXN<<1][30],fa[MAXN<<1],len[MAXN<<1],n,cnt[MAXN],rk[MAXN<<1],ans[MAXN];
char s[MAXN];
template<typename T> inline void read(T &x)
{
T data=0,w=1;
char ch=0;
while(ch!='-'&&(ch<'0'||ch>'9'))ch=getchar();
if(ch=='-')w=-1,ch=getchar();
while(ch>='0'&&ch<='9')data=((T)data<<3)+((T)data<<1)+(ch^'0'),ch=getchar();
x=data*w;
}
template<typename T> inline void write(T x,char ch='\0')
{
if(x<0)putchar('-'),x=-x;
if(x>9)write(x/10);
putchar(x%10+'0');
if(ch!='\0')putchar(ch);
}
template<typename T> inline void chkmin(T &x,T y){x=(y<x?y:x);}
template<typename T> inline void chkmax(T &x,T y){x=(y>x?y:x);}
template<typename T> inline T min(T x,T y){return x<y?x:y;}
template<typename T> inline T max(T x,T y){return x>y?x:y;}
inline void extend(int c)
{
int p=las,np=++tot;
las=np;
len[np]=len[p]+1;
while(p&&!ch[p][c])ch[p][c]=np,p=fa[p];
if(!p)fa[np]=1;
else
{
int q=ch[p][c];
if(len[q]==len[p]+1)fa[np]=q;
else
{
int nq=++tot;
fa[nq]=fa[q];
memcpy(ch[nq],ch[q],sizeof(ch[q]));
len[nq]=len[p]+1,fa[q]=fa[np]=nq;
while(p&&ch[p][c]==q)ch[p][c]=nq,p=fa[p];
}
}
size[np]=1;
}
int main()
{
scanf("%s",s+1);
n=strlen(s+1);
for(register int i=1;i<=n;++i)extend(s[i]-'a'+1);
for(register int i=1;i<=tot;++i)cnt[len[i]]++;
for(register int i=1;i<=n;++i)cnt[i]+=cnt[i-1];
for(register int i=1;i<=tot;++i)rk[cnt[len[i]]--]=i;
for(register int i=tot;i>=1;--i)size[fa[rk[i]]]+=size[rk[i]],chkmax(ans[len[rk[i]]],size[rk[i]]);
for(register int i=n;i>=1;--i)chkmax(ans[i],ans[i+1]);
for(register int i=1;i<=n;++i)write(ans[i],'\n');
return 0;
}