Querying the segment tree

Querying the segment tree.cpp

// V is the type of the required aggregate statistic
V getValue(int lo, int hi) {
  SegmentTreeNode result = getValue(1, 0, N-1, lo, hi);
  return result.getValue();
}

// nodes[stIndex] is responsible for the segment [left, right]
// and we want to query for the segment [lo, hi]
SegmentTreeNode getValue(int stIndex, int left, int right, int lo, int hi) {
  if (left == lo && right == hi)
    return nodes[stIndex];
  	
  int mid = (left + right) / 2;
  if (lo > mid)
    return getValue(2*stIndex+1, mid+1, right, lo, hi);
  if (hi <= mid)
    return getValue(2*stIndex, left, mid, lo, hi);
  	
  SegmentTreeNode leftResult = getValue(2*stIndex, left, mid, lo, mid);
  SegmentTreeNode rightResult = getValue(2*stIndex+1, mid+1, right, mid+1, hi);
  SegmentTreeNode result;
  result.merge(leftResult, rightResult);
  return result;
}