ctci/02. Linked lists/hackerrank/find_merge_point.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

public class Solution {

    static class SinglyLinkedListNode {
        public int data;
        public SinglyLinkedListNode next;

        public SinglyLinkedListNode(int nodeData) {
            this.data = nodeData;
            this.next = null;
        }
    }

    static class SinglyLinkedList {
        public SinglyLinkedListNode head;
        public SinglyLinkedListNode tail;

        public SinglyLinkedList() {
            this.head = null;
            this.tail = null;
        }

        public void insertNode(int nodeData) {
            SinglyLinkedListNode node = new SinglyLinkedListNode(nodeData);

            if (this.head == null) {
                this.head = node;
            } else {
                this.tail.next = node;
            }

            this.tail = node;
        }
    }

    public static void printSinglyLinkedList(SinglyLinkedListNode node, String sep, BufferedWriter bufferedWriter)
            throws IOException {
        while (node != null) {
            bufferedWriter.write(String.valueOf(node.data));

            node = node.next;

            if (node != null) {
                bufferedWriter.write(sep);
            }
        }
    }

    // Complete the findMergeNode function below.

    /*
     * For your reference:
     *
     * SinglyLinkedListNode { int data; SinglyLinkedListNode next; }
     *
     */

    // https://stackoverflow.com/questions/1594061/check-if-two-linked-lists-merge-if-so-where/14956113#14956113
    static int FindMergeNode(SinglyLinkedListNode headA, SinglyLinkedListNode headB) {
        SinglyLinkedListNode currentA = headA;
        SinglyLinkedListNode currentB = headB;

        // Do till the two nodes are the same
        while (currentA != currentB) {
            // If you reached the end of one list start at the beginning of the other one
            // currentA
            if (currentA.next == null) {
                currentA = headB;
            } else {
                currentA = currentA.next;
            }
            // currentB
            if (currentB.next == null) {
                currentB = headA;
            } else {
                currentB = currentB.next;
            }
        }
        return currentB.data;
    }

    private static final Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) throws IOException {
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        int tests = scanner.nextInt();
        scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

        for (int testsItr = 0; testsItr < tests; testsItr++) {
            int index = scanner.nextInt();
            scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

            SinglyLinkedList llist1 = new SinglyLinkedList();

            int llist1Count = scanner.nextInt();
            scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

            for (int i = 0; i < llist1Count; i++) {
                int llist1Item = scanner.nextInt();
                scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

                llist1.insertNode(llist1Item);
            }

            SinglyLinkedList llist2 = new SinglyLinkedList();

            int llist2Count = scanner.nextInt();
            scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

            for (int i = 0; i < llist2Count; i++) {
                int llist2Item = scanner.nextInt();
                scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

                llist2.insertNode(llist2Item);
            }

            SinglyLinkedListNode ptr1 = llist1.head;
            SinglyLinkedListNode ptr2 = llist2.head;

            for (int i = 0; i < llist1Count; i++) {
                if (i < index) {
                    ptr1 = ptr1.next;
                }
            }

            for (int i = 0; i < llist2Count; i++) {
                if (i != llist2Count - 1) {
                    ptr2 = ptr2.next;
                }
            }

            ptr2.next = ptr1;

            int result = findMergeNode(llist1.head, llist2.head);

            bufferedWriter.write(String.valueOf(result));
            bufferedWriter.newLine();
        }

        bufferedWriter.close();

        scanner.close();
    }
}