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  • 【刷题】SPOJ 8222 NSUBSTR

    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)

    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='')
    {
    	if(x<0)putchar('-'),x=-x;
    	if(x>9)write(x/10);
    	putchar(x%10+'0');
    	if(ch!='')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],'
    ');
    	return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/hongyj/p/9100317.html
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