src/string/suffix-array.hpp

• View this file on GitHub
• Last update: 2025-07-19 13:39:45+09:00
• Include: #include "src/string/suffix-array.hpp"

Verified with

• verify/string/suffix-array/number_of_substrings.test.cpp
• verify/string/suffix-array/suffixarray.test.cpp

Code

#pragma once

/**
 * Author: Teetat T.
 * Date: 2024-06-14
 * Description: Suffix Array.
 */

template<class STR>
struct SuffixArray{
    int n;
    vector<int> sa,isa,lcp;
    // SparseTable<MinMonoid<int>> st;
    SuffixArray(){}
    SuffixArray(const STR &s){init(s);}
    void init(const STR &s){
        n=(int)s.size();
        sa=isa=lcp=vector<int>(n+1);
        sa[0]=n;
        iota(sa.begin()+1,sa.end(),0);
        sort(sa.begin()+1,sa.end(),[&](int i,int j){return s[i]<s[j];});
        for(int i=1;i<=n;i++){
            int x=sa[i-1],y=sa[i];
            isa[y]=i>1&&s[x]==s[y]?isa[x]:i;
        }
        for(int len=1;len<=n;len<<=1){
            vector<int> ps(sa),pi(isa),pos(n+1);
            iota(pos.begin(),pos.end(),0);
            for(auto i:ps)if((i-=len)>=0)sa[pos[isa[i]]++]=i;
            for(int i=1;i<=n;i++){
                int x=sa[i-1],y=sa[i];
                isa[y]=pi[x]==pi[y]&&pi[x+len]==pi[y+len]?isa[x]:i;
            }
        }
        for(int i=0,k=0;i<n;i++){
            for(int j=sa[isa[i]-1];j+k<n&&s[j+k]==s[i+k];k++);
            lcp[isa[i]]=k;
            if(k)k--;
        }
        // st.init(lcp);
    }
    // int get_lcp(int i,int j){
    //     if(i==j)return n-i;
    //     auto [l,r]=minmax(isa[i],isa[j]);
    //     return st.query(l+1,r);
    // }
};

#line 2 "src/string/suffix-array.hpp"

/**
 * Author: Teetat T.
 * Date: 2024-06-14
 * Description: Suffix Array.
 */

template<class STR>
struct SuffixArray{
    int n;
    vector<int> sa,isa,lcp;
    // SparseTable<MinMonoid<int>> st;
    SuffixArray(){}
    SuffixArray(const STR &s){init(s);}
    void init(const STR &s){
        n=(int)s.size();
        sa=isa=lcp=vector<int>(n+1);
        sa[0]=n;
        iota(sa.begin()+1,sa.end(),0);
        sort(sa.begin()+1,sa.end(),[&](int i,int j){return s[i]<s[j];});
        for(int i=1;i<=n;i++){
            int x=sa[i-1],y=sa[i];
            isa[y]=i>1&&s[x]==s[y]?isa[x]:i;
        }
        for(int len=1;len<=n;len<<=1){
            vector<int> ps(sa),pi(isa),pos(n+1);
            iota(pos.begin(),pos.end(),0);
            for(auto i:ps)if((i-=len)>=0)sa[pos[isa[i]]++]=i;
            for(int i=1;i<=n;i++){
                int x=sa[i-1],y=sa[i];
                isa[y]=pi[x]==pi[y]&&pi[x+len]==pi[y+len]?isa[x]:i;
            }
        }
        for(int i=0,k=0;i<n;i++){
            for(int j=sa[isa[i]-1];j+k<n&&s[j+k]==s[i+k];k++);
            lcp[isa[i]]=k;
            if(k)k--;
        }
        // st.init(lcp);
    }
    // int get_lcp(int i,int j){
    //     if(i==j)return n-i;
    //     auto [l,r]=minmax(isa[i],isa[j]);
    //     return st.query(l+1,r);
    // }
};

Back to top page