Mo's algorithm
(misc/mo.hpp)

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• Last update: 2023-08-02 22:18:29+07:00
• Include: #include "misc/mo.hpp"

Code

#pragma once

// mo start from 1, so if query is [l, r), then insert [l - 1, r)

struct mo_algo {
  int width;
  vector<int> left, right, order;

  mo_algo(int N, int Q) : order(Q) {
    width = max<int>(1, 1.0 * N / max<double>(1.0, sqrt(Q * 2.0 / 3.0)));
    iota(begin(order), end(order), 0);
  }

  void insert(int l, int r) { /* [l, r) */
    left.emplace_back(l);
    right.emplace_back(r);
  }

  template <typename AL, typename AR, typename DL, typename DR, typename REM>
  void run(const AL &add_left, const AR &add_right, const DL &delete_left,
           const DR &delete_right, const REM &rem) {
    assert(left.size() == order.size());
    sort(begin(order), end(order), [&](int a, int b) {
      int ablock = left[a] / width, bblock = left[b] / width;
      if (ablock != bblock) return ablock < bblock;
      if (ablock & 1) return right[a] < right[b];
      return right[a] > right[b];
    });
    int nl = 0, nr = 0;
    for (auto idx : order) {
      while (nl > left[idx]) add_left(--nl);
      while (nr < right[idx]) add_right(nr++);
      while (nl < left[idx]) delete_left(nl++);
      while (nr > right[idx]) delete_right(--nr);
      rem(idx);
    }
  }
};

/**
 * @brief Mo's algorithm
 * @docs docs/misc/mo.md
 */

#line 2 "misc/mo.hpp"

// mo start from 1, so if query is [l, r), then insert [l - 1, r)

struct mo_algo {
  int width;
  vector<int> left, right, order;

  mo_algo(int N, int Q) : order(Q) {
    width = max<int>(1, 1.0 * N / max<double>(1.0, sqrt(Q * 2.0 / 3.0)));
    iota(begin(order), end(order), 0);
  }

  void insert(int l, int r) { /* [l, r) */
    left.emplace_back(l);
    right.emplace_back(r);
  }

  template <typename AL, typename AR, typename DL, typename DR, typename REM>
  void run(const AL &add_left, const AR &add_right, const DL &delete_left,
           const DR &delete_right, const REM &rem) {
    assert(left.size() == order.size());
    sort(begin(order), end(order), [&](int a, int b) {
      int ablock = left[a] / width, bblock = left[b] / width;
      if (ablock != bblock) return ablock < bblock;
      if (ablock & 1) return right[a] < right[b];
      return right[a] > right[b];
    });
    int nl = 0, nr = 0;
    for (auto idx : order) {
      while (nl > left[idx]) add_left(--nl);
      while (nr < right[idx]) add_right(nr++);
      while (nl < left[idx]) delete_left(nl++);
      while (nr > right[idx]) delete_right(--nr);
      rem(idx);
    }
  }
};

/**
 * @brief Mo's algorithm
 * @docs docs/misc/mo.md
 */

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