// Program to test solutions to problem #9 on the cse143 final, spring 2019.
// Fill in your solution to removeAlternatePairs, then compile and run the
// program

import java.util.*;

class LinkedIntList {
    public LinkedIntList removeAlternatePairs() {
        // enter solution here
    }

    private ListNode front;  // first value in the list

    // this is the sample solution
    public LinkedIntList removeAlternatePairs2() {
        LinkedIntList result = new LinkedIntList();
        if (front != null && front.next != null) {
            result.front = front;
            front = front.next.next;
            ListNode current1 = result.front.next;
            ListNode current2 = front;
            while (current2 != null && current2.next != null &&
                   current2.next.next != null &&
                   current2.next.next.next != null) {
                current1.next = current2.next.next;
                current2.next.next = current2.next.next.next.next;
                current2 = current2.next.next;
                current1 = current1.next.next;
            }
            current1.next = null;
        }
        return result;
    }

    // post: constructs an empty list
    public LinkedIntList() {
        front = null;
    }

    public boolean equals(Object o) {
        LinkedIntList other;
        try {
            other = (LinkedIntList) o;
        } catch (Exception e) {
            return false;
        }
        if (other == null) {
            return false;
        }
        ListNode current1 = front;
        ListNode current2 = other.front;
        while (current1 != null && current2 != null) {
            if (current1.data != current2.data)
                return false;
            current1 = current1.next;
            current2 = current2.next;
        }
        return current1 == null && current2 == null;
    }
        
    // post: creates a comma-separated, bracketed version of the list
    public String toString() {
        if (front == null)
            return "[]";
        else {
            String result = "[" + front.data;
            ListNode current = front.next;
            while (current != null) {
                result += ", " + current.data;
                current = current.next;
            }
            result += "]";
            return result;
        }
    }

    // post: creates a comma-separated, bracketed version of the list
    public String toString(int number) {
        if (front == null)
            return "[]";
        else {
            String result = "[" + front.data;
            int count = 1;
            ListNode current = front.next;
            while (current != null && count < number) {
                result += ", " + current.data;
                current = current.next;
                count++;
            }
            if (current != null) {
                result += "...";
            }
            result += "]";
            return result;
        }
    }

    // post: appends the given value to the end of the list
    public void add(int value) {
        if (front == null)
            front = new ListNode(value);
        else {
            ListNode current = front;
            while (current.next != null)
                current = current.next;
            current.next = new ListNode(value);
        }
    }
}

public class FinalTest9 {
    private static int totalCount = 0;
    private static int totalFail = 0;
    private static Random r = new Random();

    public static void main(String[] args) {
        for (int i = 0; i <= 20; i++) {
            test(i);
        }

        if (totalFail > 0) {
            System.out.println("failed " + totalFail + " of " + totalCount +
                               " tests");
        } else {
            System.out.println("passed all " + totalCount + " tests");
        }
    }
    
    public static void test(int len) {
        totalCount++;  // increment test counter
        // list1/list2 for testing sample, list3/list4 for their code
        LinkedIntList list1 = new LinkedIntList();
        LinkedIntList list2 = null;
        LinkedIntList list3 = new LinkedIntList();
        LinkedIntList list4 = null;
        for (int j = 0; j < len; j++) {
            int n = r.nextInt(101) - 25;
            list1.add(n);
            list3.add(n);
        }
        boolean fail = false;
        System.out.println("initial list    = " + list1);
        list2 = list1.removeAlternatePairs2();
        System.out.println("list after call = " + list1);
        System.out.println("expected result = " + list2);
        try {
            list4 = list3.removeAlternatePairs();
        } catch (RuntimeException e) {
            if(e.getStackTrace().length > 0) {
                int line = e.getStackTrace()[0].getLineNumber();
                System.out.println("    threw " + e + " at line #" + line);
            }
            fail = true;
        }
        if (!fail) {
            if (list1.equals(list3)) {
                System.out.println("your list matches");
            } else {
                System.out.println("your list       = " + 
                                   list3.toString(len));
                fail = true;
            }
            if (list2.equals(list4)) {
                System.out.println("your result matches");
            } else {
                if (list4 == null) {
                    System.out.println("your result     = null");
                } else {
                    System.out.println("your result     = " +
                                       list4.toString(len));
                }
                fail = true;
            }
        }
        if (fail) {
            System.out.println("failed");
            totalFail++;
        } else {
            System.out.println("passed");
        }
        System.out.println();
    }
}

class ListNode {
    public final int data;       // data stored in this node
    public ListNode next;  // link to next node in the list

    // post: constructs a node with data 0 and null link
    public ListNode() {
        this(0, null);
    }

    // post: constructs a node with given data and null link
    public ListNode(int data) {
        this(data, null);
    }

    // post: constructs a node with given data and given link
    public ListNode(int data, ListNode next) {
        this.data = data;
        this.next = next;
    }
}