SPOJ - LCS2

Posted 2020-10-29 walfy

后缀自动机板子题

https://vjudge.net/problem/28017/origin

找多串的最长公共子串

//#pragma comment(linker, "/stack:200000000")
//#pragma GCC optimize("Ofast,no-stack-protector")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pi acos(-1.0)
#define ll long long
#define mod (1000000007)
#define C 0.5772156649
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
#define pil pair<int,ll>
#define pii pair<int,int>
#define ull unsigned long long
#define base 1000000000000000000
#define fio ios::sync_with_stdio(false);cin.tie(0)

using namespace std;

const double g=10.0,eps=1e-12;
const int N=500000+10,maxn=1200000+10,inf=0x3f3f3f3f,INF=0x3f3f3f3f3f3f3f3f;


char s[N];
int c[N],a[N];
struct SAM{
    int last,cnt;
    int ch[N<<1][26],fa[N<<1],l[N<<1];
    int mx[N<<1],tmp[N<<1];
    void ins(int c){
        int p=last,np=++cnt;last=np;l[np]=l[p]+1;
        for(;p&&!ch[p][c];p=fa[p])ch[p][c]=np;
        if(!p)fa[np]=1;
        else
        {
            int q=ch[p][c];
            if(l[p]+1==l[q])fa[np]=q;
            else
            {
                int nq=++cnt;l[nq]=l[p]+1;
                memcpy(ch[nq],ch[q],sizeof(ch[q]));
                fa[nq]=fa[q];fa[q]=fa[np]=nq;
                for(;ch[p][c]==q;p=fa[p])ch[p][c]=nq;
            }
        }
    }
    void build(){
        int len=strlen(s+1);
        last=cnt=1;
        for(int i=1;i<=len;i++)ins(s[i]-‘a‘);
        topo();
        for(int i=1;i<=cnt;i++)mx[i]=l[i],tmp[i]=0;
    }
    void topo(){
        for(int i=1;i<=cnt;i++)c[l[i]]++;
        for(int i=1;i<=cnt;i++)c[i]+=c[i-1];
        for(int i=1;i<=cnt;i++)a[c[l[i]]--]=i;
    }
    void debug()
    {
        puts("");
        for(int i=1;i<=cnt;i++)
        {
            printf("%d ",i);
            for(int j=0;j<26;j++)
                printf("%d ",ch[i][j]);
            printf("%d %d\n",fa[i],l[i]);
        }
    }
    void faupdate()
    {
        for(int i=cnt;i;i--)
            tmp[fa[a[i]]]=max(tmp[fa[a[i]]],tmp[a[i]]);
    }
    void maupdate()
    {
        for(int i=1;i<=cnt;i++)
            mx[i]=min(mx[i],tmp[i]),tmp[i]=0;
    }
    void match()
    {
        int len=strlen(s+1),val=0,now=1,res=0;
        for(int i=1;i<=len;i++)
        {
            if(ch[now][s[i]-‘a‘])
            {
                now=ch[now][s[i]-‘a‘];
                res++;
            }
            else
            {
                while(now&&!ch[now][s[i]-‘a‘])now=fa[now];
                if(!now)now=1,res=0;
                else
                {
                    res=l[now]+1;
                    now=ch[now][s[i]-‘a‘];
                }
            }
            tmp[now]=max(tmp[now],res);
        }
        faupdate();
        maupdate();
    }
    int maxlen()
    {
        int ans=0;
        for(int i=1;i<=cnt;i++)ans=max(ans,mx[i]);
        return ans;
    }
}sam;
int main()
{
    scanf("%s",s+1);
    sam.build();
    while(~scanf("%s",s+1))
        sam.match();//,printf("%d\n",sam.maxlen());
    printf("%d\n",sam.maxlen());
    return 0;
}

/********************

********************/

View Code