text: If there are more than one elements , then recur for left and right subtrees and store the sum of values in this node
code: let mid = getMid ( ss , se ) ; st [ si ] = constructSTUtil ( arr , ss , mid , st , si * 2 + 1 ) + constructSTUtil ( arr , mid + 1 , se , st , si * 2 + 2 ) ; return st [ si ] ; }