LListC++

/*
Chapter 15 - Project 1
Directions: Write a program to remove an element from a linked list; the remove
function should take just the element to be removed. Is this function easy to
write and will it be fast? Could this be made easier or faster by adding
and additional pointer to the list?
*/

#include <ctime> // time
#include <cstdlib> // rand/NULL
#include <iostream> // cout/cin

using namespace std;


// our linked list structure, has one integer
struct LinkedList {
    int value; // our value
    LinkedList* pNextValue; // pointer to the next value
};

LinkedList* head = NULL; // global variable head (start of list)

// add value
LinkedList* addValue(int v) {
    LinkedList* pValue = new LinkedList; // allocate memory
    // int randomNum = randRange(0,100); // gen random number
    pValue->value = v; // set pointer to the random number
    pValue->pNextValue = head; // point to previous first element in list
    head = pValue; // update so that our newest value is at the beginning of list
    return pValue; // return our list
}

// traverse through list and display
void displayList() {
    LinkedList* current = head; // setting current to first element in list
    int i = 1; // keeps track
    while(current != NULL) {
        cout << "Value #" << i << ": " << current->value << ".\n";
        current = current->pNextValue; // go to next value
        i++; // increment i
    }
}

// remove an element from the linked list
void removeElement(int remValue) {
    // to remove an element, we go through the list, find the value given
    // if we find it, stop
    // to remove, disconnect the link
    // relink the two values now (ie. value 1->2->3->NULL, 2 is removed, 1->3->NULL )
    LinkedList* current = head;
    LinkedList* next = current;
    while(current != NULL) {
        if(current->value == remValue) { // if match
            break; // break out of while
        }
        else {
            cout << "Value " << current->value << " does not match " << remValue << ".\n";
            next = current; // save in case
            current = current->pNextValue; // go to next value
        }
    } // end while
    if(current == NULL) { // if we reached end of list
        cout << "Can't remove value: no match found.\n"; // no match, cant remove
    } else { // found match
        cout << "Deleting: " << current << "\n";
        delete current;
        current = next->pNextValue; // current is updated
    }
}

// main
int main() {
    srand(time(NULL)); // generate a random number
    LinkedList* listValue = addValue(3); // add a value to our linked list
    cout << "In memory, our list value is at: " << listValue << "\n"; // mem address
    cout << "Our actual value should be: " << listValue->value << "\n"; // actual value there
    cout << "Adding more values.\n";
    listValue = addValue(5);
    //listValue = addValue(10);
    //listValue = addValue(15);
    cout << "Mem address for " << listValue->value << ": " << listValue << "\n.";
    displayList();
    removeElement(5);
    displayList();
    cout << "\n";

}