utkarshl

struct node
{
	int segmentSum,bestPrefix,bestSuffix,bestSum;
	node split(node& l, node& r){}
	node merge(node& l, node& r)
	{
		segmentSum = l.segmentSum + r.segmentSum;
		bestPrefix = max( l.segmentSum + r.bestPrefix , l.bestPrefix );
		bestSuffix = max( r.segmentSum + l.bestSuffix , r.bestSuffix );
		bestSum    = max( max( l.bestSum , r.bestSum) , l.bestSuffix + r.bestPrefix );

utkarshl

void update_single_node(node& n, int new_val){
	n.val = new_val;
}
void range_update(int root, int left_most_leaf, int right_most_leaf, int u, int v, int new_val)
{
	if(u<=left_most_leaf && right_most_leaf<=v)
		return update_single_node(tree[root], new_val);
	int mid = (left_most_leaf+right_most_leaf)/2,
		left_child = root*2,
		right_child = left_child+1;