cp-library-cpp

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:heavy_check_mark: test/src/datastructure/compressed_wavelet_matrix/range_kth_smallest.test.cpp

Depends on

Code

#define PROBLEM "https://judge.yosupo.jp/problem/range_kth_smallest"

#include <iostream>

#include "library/datastructure/compressed_wavelet_matrix.hpp"

using suisen::CompressedWaveletMatrix;

constexpr int MAX_LOG = 18;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int n, q;
    std::cin >> n >> q;
    std::vector<int> a(n);
    for (auto &e : a) std::cin >> e;
    CompressedWaveletMatrix<int, MAX_LOG> wm(a);
    while (q --> 0) {
        int l, r, k;
        std::cin >> l >> r >> k;
        std::cout << wm.range_kth_smallest(l, r, k) << '\n';
    }
    return 0;
}
#line 1 "test/src/datastructure/compressed_wavelet_matrix/range_kth_smallest.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/range_kth_smallest"

#include <iostream>

#line 1 "library/datastructure/compressed_wavelet_matrix.hpp"



#include <cassert>
#include <array>
#include <type_traits>
#include <limits>

#line 1 "library/datastructure/wavelet_matrix.hpp"



#line 8 "library/datastructure/wavelet_matrix.hpp"

#line 1 "library/datastructure/bit_vector.hpp"



#include <cstdint>
#include <vector>

#line 1 "library/type_traits/type_traits.hpp"



#line 7 "library/type_traits/type_traits.hpp"

namespace suisen {
    template <typename ...Constraints> using constraints_t = std::enable_if_t<std::conjunction_v<Constraints...>, std::nullptr_t>;

    template <typename T, typename = std::nullptr_t> struct bitnum { static constexpr int value = 0; };
    template <typename T> struct bitnum<T, constraints_t<std::is_integral<T>>> { static constexpr int value = std::numeric_limits<std::make_unsigned_t<T>>::digits; };
    template <typename T> static constexpr int bitnum_v = bitnum<T>::value;
    template <typename T, size_t n> struct is_nbit { static constexpr bool value = bitnum_v<T> == n; };
    template <typename T, size_t n> static constexpr bool is_nbit_v = is_nbit<T, n>::value;

    template <typename T, typename = std::nullptr_t> struct safely_multipliable { using type = T; };
    template <typename T> struct safely_multipliable<T, constraints_t<std::is_signed<T>, is_nbit<T, 32>>> { using type = long long; };
    template <typename T> struct safely_multipliable<T, constraints_t<std::is_signed<T>, is_nbit<T, 64>>> { using type = __int128_t; };
    template <typename T> struct safely_multipliable<T, constraints_t<std::is_unsigned<T>, is_nbit<T, 32>>> { using type = unsigned long long; };
    template <typename T> struct safely_multipliable<T, constraints_t<std::is_unsigned<T>, is_nbit<T, 64>>> { using type = __uint128_t; };
    template <typename T> using safely_multipliable_t = typename safely_multipliable<T>::type;

    template <typename T, typename = void> struct rec_value_type { using type = T; };
    template <typename T> struct rec_value_type<T, std::void_t<typename T::value_type>> {
        using type = typename rec_value_type<typename T::value_type>::type;
    };
    template <typename T> using rec_value_type_t = typename rec_value_type<T>::type;

    template <typename T> class is_iterable {
        template <typename T_> static auto test(T_ e) -> decltype(e.begin(), e.end(), std::true_type{});
        static std::false_type test(...);
    public:
        static constexpr bool value = decltype(test(std::declval<T>()))::value;
    };
    template <typename T> static constexpr bool is_iterable_v = is_iterable<T>::value;
    template <typename T> class is_writable {
        template <typename T_> static auto test(T_ e) -> decltype(std::declval<std::ostream&>() << e, std::true_type{});
        static std::false_type test(...);
    public:
        static constexpr bool value = decltype(test(std::declval<T>()))::value;
    };
    template <typename T> static constexpr bool is_writable_v = is_writable<T>::value;
    template <typename T> class is_readable {
        template <typename T_> static auto test(T_ e) -> decltype(std::declval<std::istream&>() >> e, std::true_type{});
        static std::false_type test(...);
    public:
        static constexpr bool value = decltype(test(std::declval<T>()))::value;
    };
    template <typename T> static constexpr bool is_readable_v = is_readable<T>::value;
} // namespace suisen

#line 8 "library/datastructure/bit_vector.hpp"

namespace suisen {
    struct BitVector {
        explicit BitVector(int n) : n(n), nl((n >> LOG_BLOCK_L) + 1), ns((n >> LOG_BLOCK_S) + 1), cum_l(nl, 0), cum_s(ns, 0), bits(ns, 0) {}
        BitVector() : BitVector(0) {}
        template <typename Gen, constraints_t<std::is_invocable_r<bool, Gen, int>> = nullptr>
        BitVector(int n, Gen gen) : BitVector(n) {
            build(gen);
        }
        BitVector& operator=(const BitVector& bv) {
            n = bv.n, nl = bv.nl, ns = bv.ns, cum_l = bv.cum_l, cum_s = bv.cum_s, bits = bv.bits;
            return *this;
        }
        BitVector& operator=(BitVector&& bv) {
            n = bv.n, nl = bv.nl, ns = bv.ns, cum_l = std::move(bv.cum_l), cum_s = std::move(bv.cum_s), bits = std::move(bv.bits);
            return *this;
        }
        template <typename Gen, constraints_t<std::is_invocable_r<bool, Gen, int>> = nullptr>
        void build(Gen gen) {
            int i = 0;
            for (int index_s = 1; index_s < ns; ++index_s) {
                int count = cum_s[index_s - 1];
                for (; i < index_s << LOG_BLOCK_S; ++i) {
                    bool b = gen(i);
                    bits[index_s - 1] |= b << (i & MASK_S);
                    count += b;
                }
                if (index_s & ((1 << (LOG_BLOCK_L - LOG_BLOCK_S)) - 1)) {
                    cum_s[index_s] = count;
                } else {
                    int index_l = i >> LOG_BLOCK_L;
                    cum_l[index_l] = cum_l[index_l - 1] + count;
                }
            }
            for (; i < n; ++i) bits[ns - 1] |= gen(i) << (i & MASK_S);
        }
        bool operator[](int i) const {
            return (bits[i >> LOG_BLOCK_S] >> (i & MASK_S)) & 1;
        }
        // returns the i'th val (i: 0-indexed)
        bool access(int i) const {
            return (*this)[i];
        }
        // returns the number of val in [0, i)
        int rank(bool val, int i) const {
            int res_1 = cum_l[i >> LOG_BLOCK_L] + cum_s[i >> LOG_BLOCK_S] + popcount8(bits[i >> LOG_BLOCK_S] & ((1 << (i & MASK_S)) - 1));
            return val ? res_1 : i - res_1;
        }
        // returns the number of val in [l, r)
        int rank(bool val, int l, int r) const {
            return rank(val, r) - rank(val, l);
        }
        // find the index of num'th val. (num: 1-indexed). if not exists, returns default_value.
        int select(bool val, int num, int default_value = -1) const {
            int l = -1, r = n + 1;
            while (r - l > 1) {
                int m = (l + r) >> 1;
                (rank(val, m) >= num ? r : l) = m;
            }
            return r == n + 1 ? default_value : r;
        }
    private:
        static constexpr int LOG_BLOCK_L = 8;
        static constexpr int LOG_BLOCK_S = 3;
        static constexpr int MASK_S = (1 << LOG_BLOCK_S) - 1;

        int n, nl, ns;
        std::vector<int> cum_l;
        std::vector<std::uint8_t> cum_s, bits;

        static constexpr std::uint8_t popcount8(std::uint8_t x) {
            x = (x & 0b01010101) + ((x >> 1) & 0b01010101);
            x = (x & 0b00110011) + ((x >> 2) & 0b00110011);
            return (x & 0b00001111) + (x >> 4);
        }
    };
} // namespace suisen


#line 10 "library/datastructure/wavelet_matrix.hpp"

namespace suisen {
    template <typename T, int bit_num = std::numeric_limits<std::make_unsigned_t<T>>::digits>
    struct WaveletMatrix {
        // default constructor
        WaveletMatrix() noexcept : n(0) {}
        // builds WaveletMatrix from generating function typed as (int) -> T
        template <typename Gen, constraints_t<std::is_invocable_r<T, Gen, int>> = nullptr>
        WaveletMatrix(int n, Gen generator) : n(n) {
            build(generator);
        }
        // builds WaveletMatrix from vector
        template <typename U, constraints_t<std::is_constructible<T, U>> = nullptr>
        WaveletMatrix(const std::vector<U>& a) : WaveletMatrix(a.size(), [&a](int i) { return T(a[i]); }) {}

        // builds WaveletMatrix from generating function typed as (int) -> T
        template <typename Gen, constraints_t<std::is_invocable_r<T, Gen, int>> = nullptr>
        void build(Gen generator) {
            std::vector<T> a(n), l(n), r(n);
            for (int i = 0; i < n; ++i) a[i] = generator(i);
            for (int log = bit_num - 1; log >= 0; --log) {
                bv[log] = BitVector(n, [&a, log](int i) -> bool { return (a[i] >> log) & 1; });
                int li = 0, ri = 0;
                for (int i = 0; i < n; ++i) {
                    ((a[i] >> log) & 1 ? r[ri++] : l[li++]) = a[i];
                }
                a.swap(l);
                std::copy(r.begin(), r.begin() + ri, a.begin() + li);
                mid[log] = li;
            }
        }

        // returns WaveletMatrix[i]
        T operator[](int i) const {
            T res = 0;
            for (int log = bit_num - 1; log >= 0; --log) {
                bool b = bv[log][i];
                res |= T(b) << log;
                i = b * mid[log] + bv[log].rank(b, i);
            }
            return res;
        }
        // returns WaveletMatrix[i]
        T access(int i) const {
            return (*this)[i];
        }

        // returns the number of `val` in WaveletMatrix[0, i).
        int rank(T val, int i) const {
            check_value_bounds(val);
            int l = 0, r = i;
            for (int log = bit_num - 1; log >= 0; --log) succ(l, r, (val >> log) & 1, log);
            return r - l;
        }

        // returns the k'th smallest value in the multiset {| x ^ WaveletMatrix[i] : i in [l, r) |} (k : 0-indexed)
        T range_xor_kth_smallest(int l, int r, int k, T x, T default_value = T(-1)) const {
            if (k < 0 or k >= r - l) return default_value;
            T res = 0;
            check_value_bounds(x);
            for (int log = bit_num - 1; log >= 0; --log) {
                bool z = (x >> log) & 1;
                int cnt_z = bv[log].rank(z, l, r);
                bool skip_z = k >= cnt_z, bit = z ^ skip_z;
                succ(l, r, bit, log);
                res |= T(bit) << log;
                k -= skip_z * cnt_z;
            }
            return res;
        }
        // returns the k'th largest value in the multiset {| x ^ WaveletMatrix[i] : i in [l, r) |} (k : 0-indexed)
        T range_xor_kth_largest(int l, int r, int k, T x, T default_value = T(-1)) const {
            return range_xor_kth_smallest(l, r, r - l - 1 - k, x, default_value);
        }
        // returns the minimum value in the set { x ^ WaveletMatrix[i] : i in [l, r) }
        T range_xor_min(int l, int r, T x) const {
            assert(l < r);
            return range_xor_kth_smallest(l, r, 0, x);
        }
        // returns the maximum value in the set { x ^ WaveletMatrix[i] : i in [l, r) }
        T range_xor_max(int l, int r, T x) const {
            assert(l < r);
            return range_xor_kth_largest(l, r, 0, x);
        }

        // returns the number of v in WaveletMatrix[l, r) s.t. v ^ x < upper
        int range_xor_freq(int l, int r, T x, T upper) const {
            if (r <= l) return 0;
            if (upper > MAX) return r - l;
            check_value_bounds(x);
            int res = 0;
            for (int log = bit_num - 1; log >= 0; --log) {
                bool z = (x >> log) & 1, u = (upper >> log) & 1;
                if (u) res += bv[log].rank(z, l, r);
                succ(l, r, z ^ u, log);
            }
            return res;
        }
        // returns the number of v in WaveletMatrix[l, r) s.t. lower <= x ^ v < upper
        int range_xor_freq(int l, int r, T x, T lower, T upper) const {
            if (lower >= upper) return 0;
            return range_xor_freq(l, r, x, upper) - range_xor_freq(l, r, x, lower);
        }

        // returns the minimum value v in WaveletMatrix[l, r) s.t. lower <= x ^ v
        T range_xor_min_geq(int l, int r, T x, T lower, T default_value = T(-1)) const {
            int cnt = range_xor_freq(l, r, x, lower);
            return cnt >= r - l ? default_value : range_xor_kth_smallest(l, r, cnt, x);
        }
        // returns the minimum value v in WaveletMatrix[l, r) s.t. lower < x ^ v
        T range_xor_min_gt(int l, int r, T x, T lower, T default_value = T(-1)) const {
            return lower == MAX ? default_value : range_xor_min_geq(l, r, x, lower + 1, default_value);
        }
        // returns the maximum value v in WaveletMatrix[l, r) s.t. x ^ v < upper
        T range_xor_max_lt(int l, int r, T x, T upper, T default_value = T(-1)) const {
            int cnt = range_xor_freq(l, r, x, upper);
            return cnt == 0 ? default_value : range_xor_kth_smallest(l, r, cnt - 1, x, default_value);
        }
        // returns the maximum value v in WaveletMatrix[l, r) s.t. x ^ v <= upper
        T range_xor_max_leq(int l, int r, T x, T upper, T default_value = T(-1)) const {
            if (l >= r) return default_value;
            return upper == MAX ? range_xor_max(l, r, x) : range_xor_max_lt(l, r, x, upper + 1, default_value);
        }

        // returns the k'th smallest value in WaveletMatrix[l, r) (k : 0-indexed)
        T range_kth_smallest(int l, int r, int k, T default_value = T(-1)) const { return range_xor_kth_smallest(l, r, k, 0, default_value); }
        // returns the k'th largest value in WaveletMatrix[l, r) (k : 0-indexed)
        T range_kth_largest(int l, int r, int k, T default_value = T(-1)) const { return range_xor_kth_largest(l, r, k, 0, default_value); }
        // returns the minimum value in WaveletMatrix[l, r)
        T range_min(int l, int r) const { return range_xor_min(l, r, 0); }
        // returns the maximum value in WaveletMatrix[l, r)
        T range_max(int l, int r) const { return range_xor_max(l, r, 0); }

        // returns the number of v in WaveletMatrix[l, r) s.t. v < upper
        int range_freq(int l, int r, T upper) const { return range_xor_freq(l, r, 0, upper); }
        // returns the number of v in WaveletMatrix[l, r) s.t. lower <= v < upper
        int range_freq(int l, int r, T lower, T upper) const { return range_xor_freq(l, r, 0, lower, upper); }
        // returns the minimum value v in WaveletMatrix[l, r) s.t. lower <= v
        T range_min_geq(int l, int r, T lower, T default_value = T(-1)) const { return range_xor_min_geq(l, r, 0, lower, default_value); }
        // returns the minimum value v in WaveletMatrix[l, r) s.t. lower < v
        T range_min_gt(int l, int r, T lower, T default_value = T(-1)) const { return range_xor_min_gt(l, r, 0, lower, default_value); }
        // returns the maximum value v in WaveletMatrix[l, r) s.t. v < upper
        T range_max_lt(int l, int r, T upper, T default_value = T(-1)) const { return range_xor_max_lt(l, r, 0, upper, default_value); }
        // returns the maximum value v in WaveletMatrix[l, r) s.t. v <= upper
        T range_max_leq(int l, int r, T upper, T default_value = T(-1)) const { return range_xor_max_leq(l, r, 0, upper, default_value); }
    protected:
        WaveletMatrix(int n) noexcept : n(n) {}
    private:
        static_assert(bit_num > 0);
        static constexpr T MAX = bit_num == std::numeric_limits<T>::digits ? std::numeric_limits<T>::max() : (T(1) << bit_num) - 1;

        int n;
        std::array<BitVector, bit_num> bv;
        std::array<int, bit_num> mid;

        void succ(int& l, int& r, const bool b, const int log) const {
            l = b * mid[log] + bv[log].rank(b, l);
            r = b * mid[log] + bv[log].rank(b, r);
        }

        static void check_value_bounds(T val) {
            assert((val >> bit_num) == 0);
        }
    };
} // namespace suisen


#line 1 "library/util/coordinate_compressor.hpp"



#include <algorithm>
#line 7 "library/util/coordinate_compressor.hpp"

#line 9 "library/util/coordinate_compressor.hpp"

namespace suisen {
template <typename T>
class CoordinateCompressorBuilder {
    public:
        struct Compressor {
            public:
                static constexpr int absent = -1;

                // default constructor
                Compressor() : _xs(std::vector<T>{}) {}
                // Construct from strictly sorted vector
                Compressor(const std::vector<T> &xs) : _xs(xs) {
                    assert(is_strictly_sorted(xs));
                }

                // Return the number of distinct keys.
                int size() const {
                    return _xs.size();
                }
                // Check if the element is registered.
                bool has_key(const T &e) const {
                    return std::binary_search(_xs.begin(), _xs.end(), e);
                }
                // Compress the element. if not registered, returns `default_value`. (default: Compressor::absent)
                int comp(const T &e, int default_value = absent) const {
                    const int res = min_geq_index(e);
                    return res != size() and _xs[res] == e ? res : default_value;
                }
                // Restore the element from the index.
                T decomp(const int compressed_index) const {
                    return _xs[compressed_index];
                }
                // Compress the element. Equivalent to call `comp(e)`
                int operator[](const T &e) const {
                    return comp(e);
                }
                // Return the minimum registered value greater than `e`. if not exists, return `default_value`.
                T min_gt(const T &e, const T &default_value) const {
                    auto it = std::upper_bound(_xs.begin(), _xs.end(), e);
                    return it == _xs.end() ? default_value : *it;
                }
                // Return the minimum registered value greater than or equal to `e`. if not exists, return `default_value`.
                T min_geq(const T &e, const T &default_value) const {
                    auto it = std::lower_bound(_xs.begin(), _xs.end(), e);
                    return it == _xs.end() ? default_value : *it;
                }
                // Return the maximum registered value less than `e`. if not exists, return `default_value`
                T max_lt(const T &e, const T &default_value) const {
                    auto it = std::upper_bound(_xs.rbegin(), _xs.rend(), e, std::greater<T>());
                    return it == _xs.rend() ? default_value : *it;
                }
                // Return the maximum registered value less than or equal to `e`. if not exists, return `default_value`
                T max_leq(const T &e, const T &default_value) const {
                    auto it = std::lower_bound(_xs.rbegin(), _xs.rend(), e, std::greater<T>());
                    return it == _xs.rend() ? default_value : *it;
                }
                // Return the compressed index of the minimum registered value greater than `e`. if not exists, return `compressor.size()`.
                int min_gt_index(const T &e) const {
                    return std::upper_bound(_xs.begin(), _xs.end(), e) - _xs.begin();
                }
                // Return the compressed index of the minimum registered value greater than or equal to `e`. if not exists, return `compressor.size()`.
                int min_geq_index(const T &e) const {
                    return std::lower_bound(_xs.begin(), _xs.end(), e) - _xs.begin();
                }
                // Return the compressed index of the maximum registered value less than `e`. if not exists, return -1.
                int max_lt_index(const T &e) const {
                    return int(_xs.rend() - std::upper_bound(_xs.rbegin(), _xs.rend(), e, std::greater<T>())) - 1;
                }
                // Return the compressed index of the maximum registered value less than or equal to `e`. if not exists, return -1.
                int max_leq_index(const T &e) const {
                    return int(_xs.rend() - std::lower_bound(_xs.rbegin(), _xs.rend(), e, std::greater<T>())) - 1;
                }
            private:
                std::vector<T> _xs;
                static bool is_strictly_sorted(const std::vector<T> &v) {
                    return std::adjacent_find(v.begin(), v.end(), std::greater_equal<T>()) == v.end();
                }
        };
        CoordinateCompressorBuilder() : _xs(std::vector<T>{}) {}
        explicit CoordinateCompressorBuilder(const std::vector<T> &xs) : _xs(xs) {}
        explicit CoordinateCompressorBuilder(std::vector<T> &&xs) : _xs(std::move(xs)) {}
        template <typename Gen, constraints_t<std::is_invocable_r<T, Gen, int>> = nullptr>
        CoordinateCompressorBuilder(const int n, Gen generator) {
            reserve(n);
            for (int i = 0; i < n; ++i) push(generator(i));
        }
        // Attempt to preallocate enough memory for specified number of elements.
        void reserve(int n) {
            _xs.reserve(n);
        }
        // Add data.
        void push(const T &first) {
            _xs.push_back(first);
        }
        // Add data.
        void push(T &&first) {
            _xs.push_back(std::move(first));
        }
        // Add data in the range of [first, last). 
        template <typename Iterator>
        auto push(const Iterator &first, const Iterator &last) -> decltype(std::vector<T>{}.push_back(*first), void()) {
            for (auto it = first; it != last; ++it) _xs.push_back(*it);
        }
        // Add all data in the container. Equivalent to `push(iterable.begin(), iterable.end())`.
        template <typename Iterable>
        auto push(const Iterable &iterable) -> decltype(std::vector<T>{}.push_back(*iterable.begin()), void()) {
            push(iterable.begin(), iterable.end());
        }
        // Add data.
        template <typename ...Args>
        void emplace(Args &&...args) {
            _xs.emplace_back(std::forward<Args>(args)...);
        }
        // Build compressor.
        auto build() {
            std::sort(_xs.begin(), _xs.end()), _xs.erase(std::unique(_xs.begin(), _xs.end()), _xs.end());
            return Compressor {_xs};
        }
        // Build compressor from vector.
        static auto build(const std::vector<T> &xs) {
            return CoordinateCompressorBuilder(xs).build();
        }
        // Build compressor from vector.
        static auto build(std::vector<T> &&xs) {
            return CoordinateCompressorBuilder(std::move(xs)).build();
        }
        // Build compressor from generator.
        template <typename Gen, constraints_t<std::is_invocable_r<T, Gen, int>> = nullptr>
        static auto build(const int n, Gen generator) {
            return CoordinateCompressorBuilder<T>(n, generator).build();
        }
    private:
        std::vector<T> _xs;
};

} // namespace suisen


#line 11 "library/datastructure/compressed_wavelet_matrix.hpp"

namespace suisen {
    template <typename T, int log_max_len = std::numeric_limits<std::make_unsigned_t<T>>::digits>
    struct CompressedWaveletMatrix : private WaveletMatrix<int, log_max_len> {
        // default constructor
        CompressedWaveletMatrix() noexcept : WaveletMatrix<int, log_max_len>(0) {}
        // builds WaveletMatrix from generating function typed as (int) -> T
        template <typename Gen, constraints_t<std::is_invocable_r<T, Gen, int>> = nullptr>
        CompressedWaveletMatrix(int n, Gen generator) : WaveletMatrix<int, log_max_len>(n), comp(CoordinateCompressorBuilder<T>::build(n, generator)) {
            this->build([this, &generator](int i) { return comp[generator(i)]; });
        }
        // builds WaveletMatrix from vector
        template <typename U, constraints_t<std::is_constructible<T, U>> = nullptr>
        CompressedWaveletMatrix(const std::vector<U>& a) : CompressedWaveletMatrix(a.size(), [&a](int i) { return T(a[i]); }) {}

        // returns WaveletMatrix[i]
        inline T operator[](int i) const {
            return comp.decomp(WaveletMatrix<int, log_max_len>::operator[](i));
        }
        // returns WaveletMatrix[i]
        inline T access(int i) const {
            return (*this)[i];
        }
        // returns the number of `val` in WaveletMatrix[0, i).
        inline int rank(T val, int i) const {
            int x = comp.comp(val, -1);
            if (x == -1) return 0;
            return WaveletMatrix<int, log_max_len>::rank(x, i);
        }
        // returns the k'th smallest value in WaveletMatrix[l, r) (k : 0-indexed)
        inline T range_kth_smallest(int l, int r, int k, T default_value = T(-1)) const {
            int x = WaveletMatrix<int, log_max_len>::range_kth_smallest(l, r, k, -1);
            return x == -1 ? default_value : comp.decomp(x);
        }
        // returns the k'th largest value in WaveletMatrix[l, r) (k : 0-indexed)
        inline T range_kth_largest(int l, int r, int k, T default_value = T(-1)) const {
            int x = WaveletMatrix<int, log_max_len>::range_kth_largest(l, r, k, -1);
            return x == -1 ? default_value : comp.decomp(x);
        }
        // returns the minimum value in WaveletMatrix[l, r)
        inline T range_min(int l, int r) const {
            return comp.decomp(WaveletMatrix<int, log_max_len>::range_min(l, r));
        }
        // returns the maximum value in WaveletMatrix[l, r)
        inline T range_max(int l, int r) const {
            return comp.decomp(WaveletMatrix<int, log_max_len>::range_max(l, r));
        }
        // returns the number of v in WaveletMatrix[l, r) s.t. v < upper
        inline int range_freq(int l, int r, T upper) const {
            return WaveletMatrix<int, log_max_len>::range_freq(l, r, comp.min_geq_index(upper));
        }
        // returns the number of v in WaveletMatrix[l, r) s.t. lower <= v < upper
        inline int range_freq(int l, int r, T lower, T upper) const {
            if (lower >= upper) return 0;
            return range_freq(l, r, upper) - range_freq(l, r, lower);
        }
        // returns the minimum value v in WaveletMatrix[l, r) s.t. lower <= v
        inline T range_min_geq(int l, int r, T lower, T default_value = T(-1)) const {
            int x = WaveletMatrix<int, log_max_len>::range_min_geq(l, r, comp.min_geq_index(lower), -1);
            return x == -1 ? default_value : comp.decomp(x);
        }
        // returns the minimum value v in WaveletMatrix[l, r) s.t. lower < v
        inline T range_min_gt(int l, int r, T lower, T default_value = T(-1)) const {
            return lower == std::numeric_limits<T>::max() ? default_value : range_min_geq(l, r, lower + 1, default_value);
        }
        // returns the maximum value v in WaveletMatrix[l, r) s.t. v < upper
        inline T range_max_lt(int l, int r, T upper, T default_value = T(-1)) const {
            int x = WaveletMatrix<int, log_max_len>::range_max_lt(l, r, comp.min_geq_index(upper), -1);
            return x == -1 ? default_value : comp.decomp(x);
        }
        // returns the maximum value v in WaveletMatrix[l, r) s.t. v <= upper
        inline T range_max_leq(int l, int r, T upper, T default_value = T(-1)) const {
            if (r >= l) return default_value;
            return upper == std::numeric_limits<T>::max() ? range_max(l, r) : range_max_lt(l, r, upper + 1, default_value);
        }
    private:
        typename CoordinateCompressorBuilder<T>::Compressor comp;
    };
} // namespace suisen



#line 6 "test/src/datastructure/compressed_wavelet_matrix/range_kth_smallest.test.cpp"

using suisen::CompressedWaveletMatrix;

constexpr int MAX_LOG = 18;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int n, q;
    std::cin >> n >> q;
    std::vector<int> a(n);
    for (auto &e : a) std::cin >> e;
    CompressedWaveletMatrix<int, MAX_LOG> wm(a);
    while (q --> 0) {
        int l, r, k;
        std::cin >> l >> r >> k;
        std::cout << wm.range_kth_smallest(l, r, k) << '\n';
    }
    return 0;
}
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