Update fenwick_tree_2d.cpp

Changes

1 changed files (+13/-7)

• Data Structures/fenwick_tree_2d.cpp
  • @@ -1,21 +1,27 @@
    + #include <vector> + using namespace std; + class fenwick_tree_2d { - private: int N, M, vector<vector<int>> FT; + private: int N, M; vector<vector<int>> FT; public: fenwick_tree_2d(int n, int m) { N = n + 1, M = m + 1; - FT.resize(N, 0); + FT.resize(N); for (int i = 0; i < N; i++) FT[i].resize(M, 0); } void update(int x, int y, int val) { - for (int i = x; i < N; i += i & -i) { - for (int j = y; j < M; j += j & -j) FT[i][j] += val; + for (; x < N; x += x & -x) { + for (; y < M; y += y & -y) FT[x][y] += val; } } int query(int x, int y) { int ret = 0; - for (int i = x; i > 0; i -= i & -i) { - for (int j = y; j > 0; j -= j & -j) ret += FT[i][j]; + for (; x > 0; x -= x & -x) { + for (; y > 0; y -= y & -y) ret += FT[x][y]; } return ret; } - } + int query(int xl, int xr, int yl, int yr) { + return query(xr, yr) - query(xl - 1, yr) - query(xr, yl - 1) + query(xl - 1, yl - 1); + } + };