string/longest_common_prefix.hpp

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• Last update: 2022-01-08 20:23:44+09:00
• Include: #include "string/longest_common_prefix.hpp"

Depends on

• sparse_table/rmq_sparse_table.hpp
• string/suffix_array.hpp

Verified with

• string/test/run_enumerate_lyndon_rmq.test.cpp

Code

#pragma once
#include "../sparse_table/rmq_sparse_table.hpp"
#include "suffix_array.hpp"
#include <algorithm>
#include <string>
#include <utility>
#include <vector>

// CUT begin
struct LCPsparsetable {
    const int N;
    std::vector<int> sainv; // len = N
    StaticRMQ<int> rmq;
    template <typename String> LCPsparsetable(const String &s) : N(s.size()) {
        auto sa = suffix_array(s);
        auto lcp = lcp_array(s, sa);
        sainv.resize(N);
        for (int i = 0; i < N; i++) sainv[sa[i]] = i;
        rmq = {lcp, N};
    }
    int lcplen(int l1, int l2) const {
        if (l1 == l2) return N - l1;
        if (l1 == N or l2 == N) return 0;
        l1 = sainv[l1], l2 = sainv[l2];
        if (l1 > l2) std::swap(l1, l2);
        return rmq.get(l1, l2);
    }
};

#line 2 "sparse_table/rmq_sparse_table.hpp"
#include <algorithm>
#include <cassert>
#include <vector>

// CUT begin
// Range Minimum Query for static sequence by sparse table
// Complexity: $O(N \log N)$ for precalculation, $O(1)$ per query
template <typename T> struct StaticRMQ {
    inline T func(const T &l, const T &r) const noexcept { return std::min<T>(l, r); }
    int N, lgN;
    T defaultT;
    std::vector<std::vector<T>> data;
    std::vector<int> lgx_table;
    StaticRMQ() = default;
    StaticRMQ(const std::vector<T> &sequence, T defaultT)
        : N(sequence.size()), defaultT(defaultT) {
        lgx_table.resize(N + 1);
        for (int i = 2; i < N + 1; i++) lgx_table[i] = lgx_table[i >> 1] + 1;
        lgN = lgx_table[N] + 1;
        data.assign(lgN, std::vector<T>(N, defaultT));
        data[0] = sequence;
        for (int d = 1; d < lgN; d++) {
            for (int i = 0; i + (1 << d) <= N; i++) {
                data[d][i] = func(data[d - 1][i], data[d - 1][i + (1 << (d - 1))]);
            }
        }
    }
    T get(int l, int r) const { // [l, r), 0-indexed
        assert(l >= 0 and r <= N);
        if (l >= r) return defaultT;
        int d = lgx_table[r - l];
        return func(data[d][l], data[d][r - (1 << d)]);
    }
};
#line 4 "string/suffix_array.hpp"
#include <numeric>
#include <string>
#line 7 "string/suffix_array.hpp"

// CUT begin
// Suffix array algorithms from AtCoder Library
// Document: <https://atcoder.github.io/ac-library/master/document_ja/string.html>
namespace internal {

std::vector<int> sa_naive(const std::vector<int> &s) {
    int n = int(s.size());
    std::vector<int> sa(n);
    std::iota(sa.begin(), sa.end(), 0);
    std::sort(sa.begin(), sa.end(), [&](int l, int r) {
        if (l == r) return false;
        while (l < n && r < n) {
            if (s[l] != s[r]) return s[l] < s[r];
            l++, r++;
        }
        return l == n;
    });
    return sa;
}

std::vector<int> sa_doubling(const std::vector<int> &s) {
    int n = int(s.size());
    std::vector<int> sa(n), rnk = s, tmp(n);
    std::iota(sa.begin(), sa.end(), 0);
    for (int k = 1; k < n; k *= 2) {
        auto cmp = [&](int x, int y) {
            if (rnk[x] != rnk[y]) return rnk[x] < rnk[y];
            int rx = x + k < n ? rnk[x + k] : -1;
            int ry = y + k < n ? rnk[y + k] : -1;
            return rx < ry;
        };
        std::sort(sa.begin(), sa.end(), cmp);
        tmp[sa[0]] = 0;
        for (int i = 1; i < n; i++) {
            tmp[sa[i]] = tmp[sa[i - 1]] + (cmp(sa[i - 1], sa[i]) ? 1 : 0);
        }
        std::swap(tmp, rnk);
    }
    return sa;
}

// SA-IS, linear-time suffix array construction
// Reference:
// G. Nong, S. Zhang, and W. H. Chan,
// Two Efficient Algorithms for Linear Time Suffix Array Construction
template <int THRESHOLD_NAIVE = 10, int THRESHOLD_DOUBLING = 40>
std::vector<int> sa_is(const std::vector<int> &s, int upper) {
    int n = int(s.size());
    if (n == 0) return {};
    if (n == 1) return {0};
    if (n == 2) {
        if (s[0] < s[1]) {
            return {0, 1};
        } else {
            return {1, 0};
        }
    }
    if (n < THRESHOLD_NAIVE) { return sa_naive(s); }
    if (n < THRESHOLD_DOUBLING) { return sa_doubling(s); }

    std::vector<int> sa(n);
    std::vector<bool> ls(n);
    for (int i = n - 2; i >= 0; i--) {
        ls[i] = (s[i] == s[i + 1]) ? ls[i + 1] : (s[i] < s[i + 1]);
    }
    std::vector<int> sum_l(upper + 1), sum_s(upper + 1);
    for (int i = 0; i < n; i++) {
        if (!ls[i]) {
            sum_s[s[i]]++;
        } else {
            sum_l[s[i] + 1]++;
        }
    }
    for (int i = 0; i <= upper; i++) {
        sum_s[i] += sum_l[i];
        if (i < upper) sum_l[i + 1] += sum_s[i];
    }

    auto induce = [&](const std::vector<int> &lms) {
        std::fill(sa.begin(), sa.end(), -1);
        std::vector<int> buf(upper + 1);
        std::copy(sum_s.begin(), sum_s.end(), buf.begin());
        for (auto d : lms) {
            if (d == n) continue;
            sa[buf[s[d]]++] = d;
        }
        std::copy(sum_l.begin(), sum_l.end(), buf.begin());
        sa[buf[s[n - 1]]++] = n - 1;
        for (int i = 0; i < n; i++) {
            int v = sa[i];
            if (v >= 1 && !ls[v - 1]) { sa[buf[s[v - 1]]++] = v - 1; }
        }
        std::copy(sum_l.begin(), sum_l.end(), buf.begin());
        for (int i = n - 1; i >= 0; i--) {
            int v = sa[i];
            if (v >= 1 && ls[v - 1]) { sa[--buf[s[v - 1] + 1]] = v - 1; }
        }
    };

    std::vector<int> lms_map(n + 1, -1);
    int m = 0;
    for (int i = 1; i < n; i++) {
        if (!ls[i - 1] && ls[i]) { lms_map[i] = m++; }
    }
    std::vector<int> lms;
    lms.reserve(m);
    for (int i = 1; i < n; i++) {
        if (!ls[i - 1] && ls[i]) { lms.push_back(i); }
    }

    induce(lms);

    if (m) {
        std::vector<int> sorted_lms;
        sorted_lms.reserve(m);
        for (int v : sa) {
            if (lms_map[v] != -1) sorted_lms.push_back(v);
        }
        std::vector<int> rec_s(m);
        int rec_upper = 0;
        rec_s[lms_map[sorted_lms[0]]] = 0;
        for (int i = 1; i < m; i++) {
            int l = sorted_lms[i - 1], r = sorted_lms[i];
            int end_l = (lms_map[l] + 1 < m) ? lms[lms_map[l] + 1] : n;
            int end_r = (lms_map[r] + 1 < m) ? lms[lms_map[r] + 1] : n;
            bool same = true;
            if (end_l - l != end_r - r) {
                same = false;
            } else {
                while (l < end_l) {
                    if (s[l] != s[r]) { break; }
                    l++;
                    r++;
                }
                if (l == n || s[l] != s[r]) same = false;
            }
            if (!same) rec_upper++;
            rec_s[lms_map[sorted_lms[i]]] = rec_upper;
        }

        auto rec_sa = sa_is<THRESHOLD_NAIVE, THRESHOLD_DOUBLING>(rec_s, rec_upper);

        for (int i = 0; i < m; i++) { sorted_lms[i] = lms[rec_sa[i]]; }
        induce(sorted_lms);
    }
    return sa;
}

} // namespace internal

std::vector<int> suffix_array(const std::vector<int> &s, int upper) {
    assert(0 <= upper);
    for (int d : s) { assert(0 <= d && d <= upper); }
    auto sa = internal::sa_is(s, upper);
    return sa;
}

template <class T> std::vector<int> suffix_array(const std::vector<T> &s) {
    int n = int(s.size());
    std::vector<int> idx(n);
    iota(idx.begin(), idx.end(), 0);
    sort(idx.begin(), idx.end(), [&](int l, int r) { return s[l] < s[r]; });
    std::vector<int> s2(n);
    int now = 0;
    for (int i = 0; i < n; i++) {
        if (i && s[idx[i - 1]] != s[idx[i]]) now++;
        s2[idx[i]] = now;
    }
    return internal::sa_is(s2, now);
}

std::vector<int> suffix_array(const std::string &s) {
    int n = int(s.size());
    std::vector<int> s2(n);
    for (int i = 0; i < n; i++) { s2[i] = s[i]; }
    return internal::sa_is(s2, 255);
}

// Reference:
// T. Kasai, G. Lee, H. Arimura, S. Arikawa, and K. Park,
// Linear-Time Longest-Common-Prefix Computation in Suffix Arrays and Its
// Applications
template <class T>
std::vector<int> lcp_array(const std::vector<T> &s, const std::vector<int> &sa) {
    int n = int(s.size());
    assert(n >= 1);
    std::vector<int> rnk(n);
    for (int i = 0; i < n; i++) { rnk[sa[i]] = i; }
    std::vector<int> lcp(n - 1);
    int h = 0;
    for (int i = 0; i < n; i++) {
        if (h > 0) h--;
        if (rnk[i] == 0) continue;
        int j = sa[rnk[i] - 1];
        for (; j + h < n && i + h < n; h++) {
            if (s[j + h] != s[i + h]) break;
        }
        lcp[rnk[i] - 1] = h;
    }
    return lcp;
}

std::vector<int> lcp_array(const std::string &s, const std::vector<int> &sa) {
    int n = int(s.size());
    std::vector<int> s2(n);
    for (int i = 0; i < n; i++) { s2[i] = s[i]; }
    return lcp_array(s2, sa);
}

// Count keyword occurence in str
// Complexity: O(min(|str|, |keyword|) * lg |str|)
int count_keyword_occurence(const std::string &str, const std::vector<int> &suffarr,
                            const std::string &keyword) {
    const int n = str.size(), m = keyword.size();
    assert(n == suffarr.size());
    if (n < m) return 0;
    auto f1 = [&](int h) {
        for (int j = 0; h + j < n and j < m; j++) {
            if (str[h + j] < keyword[j]) return true;
            if (str[h + j] > keyword[j]) return false;
        }
        return n - h < m;
    };
    auto f2 = [&](int h) {
        for (int j = 0; h + j < n and j < m; j++) {
            // if (str[h + j] < keyword[j]) return true;
            if (str[h + j] > keyword[j]) return false;
        }
        return true;
    };
    const auto L = std::partition_point(suffarr.begin(), suffarr.end(), f1);
    const auto R = std::partition_point(L, suffarr.end(), f2);
    return std::distance(L, R);
    // return std::vector<int>(L, R); // if you need occurence positions
}
#line 6 "string/longest_common_prefix.hpp"
#include <utility>
#line 8 "string/longest_common_prefix.hpp"

// CUT begin
struct LCPsparsetable {
    const int N;
    std::vector<int> sainv; // len = N
    StaticRMQ<int> rmq;
    template <typename String> LCPsparsetable(const String &s) : N(s.size()) {
        auto sa = suffix_array(s);
        auto lcp = lcp_array(s, sa);
        sainv.resize(N);
        for (int i = 0; i < N; i++) sainv[sa[i]] = i;
        rmq = {lcp, N};
    }
    int lcplen(int l1, int l2) const {
        if (l1 == l2) return N - l1;
        if (l1 == N or l2 == N) return 0;
        l1 = sainv[l1], l2 = sainv[l2];
        if (l1 > l2) std::swap(l1, l2);
        return rmq.get(l1, l2);
    }
};

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