segment_tree_query.cpp

int query(int node, int b, int e, int l, int r) {
  // no overlap
  if (b > r || e < l) return 0;
  
  // total overlap
  if (b >= l && e <= r) return tree[node];
  
  // partial overlap
  int left = 2*node;
  int right = 2*node + 1;
  int mid = (b + e)/2;
  
  int p1 = query(left, b, mid, l, r);
  int p2 = query(right, mid + 1, e, l, r);
  return p1 + p2;
}