Method sum

Data Structures/Wavelet Tree.cpp:73–78

sum of numbers in [l ,r] less than or equal to k

  }
  //sum of numbers in [l ,r] less than or equal to k
  int sum(int l, int r, int k) {
    if(l > r or k < lo) return 0;
    if(hi <= k) return c[r] - c[l - 1];
    int lb = b[l - 1], rb = b[r];
    return this->l->sum(lb + 1, rb, k) + this->r->sum(l - lb, r - rb, k);
  }
  ~wavelet_tree() {
    delete l;
    delete r;