Solution 2 java

package com.google.challenges;
import java.util.Stack;

public class Answer {
    static class BinTree {
        int total;
        int[] nodes;
        Stack<Integer> values = new Stack();
        BinTree(int x) {
            total = (int) Math.pow(2, x) - 1;
            nodes = new int[total];
            //Populate Nodes List
            for (int i = 0, j = total; i < total; i++, j--) {
                nodes[i] = -2;
                values.add(j);
            }
            postOrder(0);
        }
        int eval(int i) {
            if ( i == -1)
            {
                return -1;
            }
            if (i > total-1)
            {
                return -1;
            }
            else
            {
                return nodes[i];
            }
        }
        boolean hasChild(int i) {
            int l = Lchild(i);
            int r = Rchild(i);
            if (l > total - 1 && r > total - 1) {
                return false;
            }
            else
            {
                return true;
            }
        }
        void populateNode(int i){
            int v = values.pop();
            nodes[i] = v;
        }
        void postOrder(int i){
            if (!hasChild(i))
            {
                populateNode(i);
            }
            else
            {
                postOrder(Lchild(i));
                postOrder(Rchild(i));
                populateNode(i);
            }
        }
        int Lchild(int i) {
            return(i*2)+1;
        }
        int Rchild(int i){
            return(i+1)*2;
        }
    }
    public static int parentIndex(int i) {
        int p =(i-1)/2;
        if(i == 0)
        {
            return -1;
        }
        else{
            return p;
        }
    }
    public static int find(int[]array, int x){
        for(int i = 0; i<array.length; i++)
        {
            if (array[i] == x)
            {
                return i;
            }
        }
        return -1;
    }
    public static int[] answer(int h, int[] q) {
        BinTree tree = new BinTree(h);
        int rootVal = tree.nodes[0];
        int[] output = new int[q.length];
        int[] temp = new int[q.length];
        for (int i =0; i < q.length; i++)
        {
            temp[i] = parentIndex(find(tree.nodes, q[i]));
        }
        for (int i =0; i < q.length; i++)
        {
            output[i] = tree.eval(temp[i]);
        }
        delete tree;
        return output;
    }
}