Range update

Range update.cpp

void update(int stIndex, int start, int end, UpdateType value) {
  if (start == end) {
    nodes[stIndex].applyUpdate(value);
    return;
  }
  
  int mid = (nodes[stIndex].start + nodes[stIndex].end) / 2,
      leftChildIndex = 2 * stIndex,
      rightChildIndex = leftChildIndex + 1;
      
  if (start > mid)
    update(rightChildIndex, start, end, value);
  else if (end <= mid)
    update(leftChildIndex, start, end, value);
  else {
    update(leftChildIndex, start, mid, value);
    update(rightChildIndex, mid+1, end, value);
  }
  nodes[stIndex].merge(nodes[leftChildIndex], nodes[rightChildIndex]);
}