Fenwick tree (Add)
(Mylib/DataStructure/FenwickTree/fenwick_tree_add.cpp)

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• Last update: 2021-04-23 23:44:44+09:00
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Operations

Requirements

Notes

Problems

References

Required by

• Range inversions query (Mylib/Typical/range_inversions_query.cpp)
• Range set query (Mylib/Typical/range_set_query.cpp)

Verified with

• test/yosupo-judge/static_range_inversions_query/main.test.cpp

Code

#pragma once
#include <cassert>
#include <vector>

namespace haar_lib {
  template <typename T>
  class fenwick_tree_add {
  public:
    using value_type = T;

  private:
    int size_;
    std::vector<value_type> data_;

  public:
    fenwick_tree_add() {}
    fenwick_tree_add(int size) : size_(size), data_(size + 1, 0) {}

    void update(int i, value_type val) {
      assert(0 <= i and i < size_);
      i += 1;  // 1-index

      while (i <= size_) {
        data_[i] = data_[i] + val;
        i += i & (-i);
      }
    }

    value_type fold(int i) const {  // [0, i)
      assert(0 <= i and i <= size_);
      value_type ret = 0;

      while (i > 0) {
        ret = ret + data_[i];
        i -= i & (-i);
      }

      return ret;
    }

    value_type fold(int l, int r) const {  // [l, r)
      assert(0 <= l and l <= r and r <= size_);
      return fold(r) - fold(l);
    }

    value_type operator[](int x) const {
      return fold(x, x + 1);
    }
  };
}  // namespace haar_lib

#line 2 "Mylib/DataStructure/FenwickTree/fenwick_tree_add.cpp"
#include <cassert>
#include <vector>

namespace haar_lib {
  template <typename T>
  class fenwick_tree_add {
  public:
    using value_type = T;

  private:
    int size_;
    std::vector<value_type> data_;

  public:
    fenwick_tree_add() {}
    fenwick_tree_add(int size) : size_(size), data_(size + 1, 0) {}

    void update(int i, value_type val) {
      assert(0 <= i and i < size_);
      i += 1;  // 1-index

      while (i <= size_) {
        data_[i] = data_[i] + val;
        i += i & (-i);
      }
    }

    value_type fold(int i) const {  // [0, i)
      assert(0 <= i and i <= size_);
      value_type ret = 0;

      while (i > 0) {
        ret = ret + data_[i];
        i -= i & (-i);
      }

      return ret;
    }

    value_type fold(int l, int r) const {  // [l, r)
      assert(0 <= l and l <= r and r <= size_);
      return fold(r) - fold(l);
    }

    value_type operator[](int x) const {
      return fold(x, x + 1);
    }
  };
}  // namespace haar_lib

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