LinkedList example

LinkedList.cpp

//
//  LinkedList.c
//  linked_lists
//
//  Created by Martyn Chamberlin on 2/5/15.
//  Copyright (c) 2015 Martyn Chamberlin. All rights reserved.
//

#include "LinkedList.h"
#include <iostream>
#include <fstream>
using namespace std;

// Have to initialize static object properties
LinkedList * LinkedList::head = new LinkedList();

LinkedList::LinkedList() {
    
}

LinkedList::LinkedList( int num ) {
    this->num = num;
}

bool LinkedList::number_already_exists( int num ) {
    LinkedList * link = head;
    while ( link != 0 ) {
        if ( link->num == num ) {
            ofstream myfile;
            myfile.open ("/users/martynchamberlin/desktop/duplicates.txt", fstream::app|fstream::out);
            myfile << num << endl;
            myfile.close();
            return true;
        }
        link = link->next;
    }
    return false;
}

void LinkedList::put_new_item_in_proper_order(int num ) {
    if ( number_already_exists( num ) ) return;
    
    LinkedList * current = LinkedList::head;
    LinkedList * newItem = new LinkedList( num );
    
    // First, check if we need to insert at the beginning
    if ( LinkedList::head->num > num ) {
        // Insert newItem at the front
        newItem->next = LinkedList::head;
        LinkedList::head = newItem;
        return;
    }
    
    // Check if we need to insert it in the middle
    while( current->next != 0 ) {
        // This condition is only satsified if the linked list contains more than
        // one item and the num contains a value that's not at either extreme
        if ( current->next->num > num ) {
            // Insert between current and next
            newItem->next = current->next;
            current->next = newItem;
            return;
        }
        current = current->next;
    }
    // If we haven't inserted it yet, that means we need to insert newItem at the end
    newItem->next = 0;
    current->next = newItem;
}

LinkedList.h

//
//  test.h
//  linked_lists
//
//  Created by Martyn Chamberlin on 2/5/15.
//  Copyright (c) 2015 Martyn Chamberlin. All rights reserved.
//

#ifndef linked_lists_test_h
#define linked_lists_test_h

class LinkedList {
public:
    LinkedList();
    LinkedList( int num );
    bool static number_already_exists(int num);
    void static put_new_item_in_proper_order(int num );
    void static print_duplicates();
    LinkedList static * head;
    LinkedList * next;
    int num;
};

#endif

main.cpp

//
//  main.cpp
//  linked_lists
//
//  Created by Martyn Chamberlin on 2/5/15.
//  Copyright (c) 2015 Martyn Chamberlin. All rights reserved.
//

#include <iostream>
#include "LinkedList.h"

using namespace std;

int main(int argc, const char * argv[]) {
    
    const int length = 20;
    
    int randomArray[length];
    
    // This gives us more random numbers. Without this we are getting the
    // same set of random numbers every time
    
    srand(time(NULL));
    
    // Initially generate 20 random numbers and store them in a generic array
    cout << "These are the random numbers as they appeared in the array" << endl;
    for ( int i = 0; i < length; i++ ) {
        randomArray[i] = rand() % 58 + 1;
        cout << randomArray[ i ] << endl;
    }
    cout << endl;
    
    // Copy the 20 random numbers and put them into the linked list. Don't store
    // any duplicates and put them in their proper sequence
    LinkedList::head->num = randomArray[ 0 ];
    LinkedList::head->next = 0;
    
    for ( int i = 1; i < length; i++ ) {
        LinkedList::put_new_item_in_proper_order(randomArray[i]);
    }
    
    LinkedList * link = LinkedList::head;
    
    // Let's print out the linked list
    cout << endl << "These are the random numbers as they appeared in the linked list" << endl;
    while ( link != 0 ) {
        cout << link->num << endl;
        link = link->next;
    }
    return 0;
}