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