HackerEarth Minimize the value problem solution

1. The tree remains binary after adding the node to the tree.
2. After applying the wave operation to this tree (the tree after adding node with value X), the sum of tree is minimum.

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.FilterInputStream;
import java.io.BufferedInputStream;
import java.util.LinkedList;
import java.util.ArrayList;
import java.io.InputStream;

public class Main {
    public static void main(String[] args) {
        new Thread(null, new Runnable() {
            public void run() {
                new Main().solve();
            }
        }, "1", 1 << 26).start();
    }

    void solve() {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        ScanReader in = new ScanReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Minimisethemagic solver = new Minimisethemagic();
        solver.solve(1, in, out);
        out.close();
    }

    static class Minimisethemagic {
        private ArrayList<Integer>[] arrayList;
        private int[] array;
        private long[] ans_ar;

        private int bfs(int node) {
            LinkedList<Integer> linkedList = new LinkedList<>();
            linkedList.add(1);
            while (linkedList.size() != 0) {
                int temp = linkedList.remove(0);
                if (temp == 1) {
                    if (arrayList[1].size() < 2) return 1;
                    if (arrayList[1].size() > 2) throw new RuntimeException();
                } else {
                    if (arrayList[temp].size() < 3) return temp;
                    if (arrayList[temp].size() > 3) throw new RuntimeException();
                }

                for (int i = 0; i < arrayList[temp].size(); i++) {
                    linkedList.add(arrayList[temp].get(i));
                }
            }
            return -1;
        }

        private long findIt(int node, int p) {
            long temp = array[node];
            for (int i = 0; i < arrayList[node].size(); i++) {
                if (arrayList[node].get(i) == p) continue;
                temp += findIt(arrayList[node].get(i), node);
            }
            return ans_ar[node] = temp;
        }

        public void solve(int testNumber, ScanReader in, PrintWriter out) {
            int n = in.scanInt();
            if (n < 1 || n > 100000) throw new RuntimeException();
            int value = in.scanInt();
            if (value < 1 || value > 1000000000) throw new RuntimeException();
            array = new int[n + 2];
            arrayList = new ArrayList[n + 2];
            ans_ar = new long[n + 2];
            for (int i = 0; i <= n + 1; i++) arrayList[i] = new ArrayList<>();
            for (int i = 1; i <= n; i++)
                if ((array[i] = in.scanInt()) < 1 || array[i] > 1000000000) throw new RuntimeException();
            array[n + 1] = value;
            for (int i = 0; i < n - 1; i++) {
                int x = in.scanInt();
                int y = in.scanInt();
                arrayList[x].add(y);
                arrayList[y].add(x);
            }
            int node = bfs(1);
            if (node == -1) throw new RuntimeException("Really ? ");
            arrayList[node].add(n + 1);
            findIt(1, -1);
            long ans = 0;
            for (int i = 0; i <= n + 1; i++) ans += ans_ar[i];
            out.println(ans);
        }

    }

    static class ScanReader {
        private byte[] buf = new byte[4 * 1024];
        private int index;
        private BufferedInputStream in;
        private int total;

        public ScanReader(InputStream inputStream) {
            in = new BufferedInputStream(inputStream);
        }

        private int scan() {
            if (index >= total) {
                index = 0;
                try {
                    total = in.read(buf);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                if (total <= 0) return -1;
            }
            return buf[index++];
        }

        public int scanInt() {
            int integer = 0;
            int n = scan();
            while (isWhiteSpace(n)) n = scan();
            int neg = 1;
            if (n == '-') {
                neg = -1;
                n = scan();
            }
            while (!isWhiteSpace(n)) {
                if (n >= '0' && n <= '9') {
                    integer *= 10;
                    integer += n - '0';
                    n = scan();
                }
            }
            return neg * integer;
        }

        private boolean isWhiteSpace(int n) {
            if (n == ' ' || n == 'n' || n == 'r' || n == 't' || n == -1) return true;
            else return false;
        }

    }
}