Replace with sum of greater node

#1 
private void modifyBSTwithgreaterelementssum(Node node, int[] sum) {
    if(node == null)
        return;
    modifyBSTwithgreaterelementssum(node.right, sum);
    sum[0]+=node.data;
    node.data = sum[0];
    modifyBSTwithgreaterelementssum(node.left, sum);
}

how this function replace node with greater element??
in this function we pass sum and node as recursive call and after calling it changes the sum[0] value but function does not return any thing when recursive call complete then previous function sum value is not change, why it is change?

#2

hi @abhishekg
sum[0] is acting as a global variable its not necessary to use a an array.
sum[0] is storing the sum of every node as it travels and updating the value the at node.

#3

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#4

when function call back then then it destroy all variable and array then how it work as global variable please explain ???

#5

@abhishekg,
the scope of the global variable is through out the code. If you call a function, the values in the global variable remain intact and are updated with every execution of the code instead of being destroyed when the function ends.

#6

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