Linked List and Array List Implementation

lists.cpp

#include <iostream>
#include <cstdio>
using namespace std;


const int MAX = 10;
// MAX specifies the maximum size the list can take
// in the array case.
// compares two strings according to Alphabetical order
// if a string is greater than the other returns 1
// if less return -1
// otherwise 0
// if a string is a substring of the other
// the largest is greater so:
// aaaa > aaa > aa > a
// a > b and a == a
// ab < aa and aa = aa
// ..

int str_compare(char *a, char *b) {
    int i = 0;
    while (true) {
        if (a[i] == '\0' && b[i] == '\0') {
            return 0;
        } else if (b[i] == '\0' || a[i] > b[i]) {
            return 1;
        } else if (a[i] == '\0' || a[i] < b[i]) {
            return -1;
        } else i++;
    }
}
namespace PartA {
    // we used separate name spaces
    // for array and pointer implementation

    typedef struct List {
        char *names[MAX];
        // a string field to hold names.
        int size;
        // size of the List must not exceed MAX;
        // usually with array lists (Like in Java) it has a capacity variable
        // that increases whenever the list is near to be full
        // and copies old data to a new array with a larger capacity
    } List;
    // list is passed by reference
    // so a change that happens within the function
    // changes the list (not its copy)

    int init(List &l) {
        l.size = 0;
        // initialize the list by setting size to 0
        // the list is initially empty
    }
    // inserts a name:"string" at position p
    // With few constrains
    // p should be between 0 and list size otherwise p is out of range
    // The name added should be less or equal names[p] and if p not equal to 0
    // name must be greater or equal to names[p-1]
    // otherwise adding the name will make the list unordered

    void insert(List &list, int p, char *name) {
        if (list.size < MAX) {
            if (p <= list.size && p >= 0) {
                if (list.size == 0 && p == 0) {
                    list.names[0] = name;
                    list.size++;
                } else if (p == list.size && str_compare(name, list.names[p - 1]) >= 0) {
                    list.names[list.size] = name;
                    list.size++;
                } else {
                    if ((p == 0 && str_compare(name, list.names[p]) <= 0) || (str_compare(name, list.names[p]) <= 0 && str_compare(name,
                            list.names[p - 1]) >= 0)
                            ) {
                        for (int i = list.size; i >= p; i--)
                            list.names[i + 1] = list.names[i];
                        // shift names to the right of the list starting from p to
                        // list size
                        list.names[p] = name;
                        list.size++;
                        // a name element is added so the list size is increased
                    } else {
                        cout << "Cannot insert a new name to maintain the list order" << endl;
                    }
                }
            } else {
                cout << "Position is out of list range" << endl;
            }
        } else {
            cout << "List is full can't add more elements" << endl;
        }
    }
    // remove an element from the list if it's
    // between the start of the list and its end
    // otherwise we can't delete an element that's not in the list
    //

    void remove(List &list, int p) {
        if (p < list.size && p >= 0) {
            for (int i = p; i < list.size - 1; i++)
                list.names[i] = list.names[i + 1];
            // shift the list to the left until p
            list.size--;
            // and decrement size because name
            // at position p is deleted
        } else {
            cout << "Position is out of list range" << endl;
        }
    }
    // a simple linear search to stop when
    // we find an occurrence of name in the list
    // returns it's index in the list
    // if not found returns -1

    int find(List &list, char* name) {
        for (int i = 0; i < list.size; i++) {
            if (str_compare(list.names[i], name) == 0) {
                return i;
            }
        }
        return -1;
    }
    // print the list in increasing order

    void traverseForward(List list) {
        if (list.size != 0) {
            cout << "List(forward): [ ";
            for (int i = 0; i < list.size; i++) {
                cout << list.names[i] << " ";
            }
            cout << "]" << endl;
        } else {
            cout << "List is empty" << endl;
        }
    }
    // print the list in decreasing order

    void traverseBackward(List list) {
        if (list.size != 0) {
            cout << "List(backward): [ ";
            for (int i = list.size - 1; i >= 0; i--) {
                cout << list.names[i] << " ";
            }
            cout << "]" << endl;
        } else {
            cout << "List is empty" << endl;
        }
    }
}
namespace PartB {
    // the name space of part B pointer implementation

    struct ListItem {
        char *name;
        // a string field to represent cell value.
        ListItem *next;
        // a pointer to the next cell (to be linked to)
    };
    typedef ListItem* LinkedList;
    // defining a linked list (pointer to cells)

    int init(LinkedList &list) {
        list = NULL;
    }
    // initially the list is empty
    // so it points to NULL (no cell)

    // Same as in the array implementation we have to respect the same conditions

    void insert(LinkedList &list, int p, char *name) {
        if (p == 0) {
            if (list == NULL || str_compare(name, list->name) <= 0) {
                // if the cell is added to the head of the list
                // we only need to check if the new cell
                // has a name less or equal to the current head cell name
                // if the list is empty we don't need to compare
                LinkedList item = new ListItem;
                item->name = name;
                item->next = list;
                list = item;
            } else {
                cout << "Cannot insert a new name to maintain the list order" << endl;
            }
        } else {
            LinkedList temp = list;
            // create a new pointer temp to not change the original list
            int count = 0;
            // count to keep track of the current position in the list
            while (count < p - 1 && temp != NULL) {
                // if current position is less than p - 1 stop the loop
                // or stop it when temp == NULL (end of the list)
                temp = temp->next;
                // next cell is assigned to current cell
                // traverse the list
                count++;
            }
            if (temp != NULL) {
                if (temp->next == NULL && str_compare(name, temp->name) >= 0 ||
                        // if it's the tail of the list
                        // just compare with the old tail cell
                        (str_compare(name, temp->name) >= 0
                        && str_compare(name, temp->next->name) <= 0)
                        // if not the tail nor the head cell of the list
                        // we need to compare with cellp and cellp+1
                        ) {
                    LinkedList item = new ListItem;
                    item->name = name;
                    item->next = temp->next;
                    temp->next = item;
                    // old list cellp-1 -> cellp ->cellp+1
                    // new list cellp-1 -> newcell -> cellp->cellp+1
                } else {
                    cout << "Cannot insert a new name to maintain the list order" << endl;
                }
            } else {
                cout << "position out of list range" << endl;
            }
        }
    }
    // delete a cell from the list
    //

    void remove(LinkedList &list, int p) {
        LinkedList temp = list;
        int count = 0;
        if (list != NULL) {
            if (p == 0) {
                LinkedList temp2 = temp;
                temp = temp->next;
                delete temp2;
            } else {
                while (count < p - 1 && temp != NULL) {
                    temp = temp->next;
                    count++;
                }
                if (temp != NULL) {
                    LinkedList temp2 = temp->next;
                    temp->next = temp2->next;
                    delete temp2;
                } else {
                    cout << "position out of list range" << endl;
                }
            }
        } else {
            cout << "The list is empty" << endl;
        }
    }
    //print the content of the list in increasing order

    void traverseForward(LinkedList list) {
        if (list != NULL) {
            cout << "List (forward)[ ";
            while (list != NULL) {
                cout << list->name << " ";
                list = list->next;
            }
            cout << "]" << endl;
        } else {
            cout << "The list is empty" << endl;
        }
    }
    // needed to print the list in backward
    // because the cout statement isn't reached until
    // the tail of the list is reached
    // then it prints the list in reverse

    void traverse_recursive(LinkedList list) {
        if (list != NULL) {
            traverse_recursive(list->next);
            cout << list->name << " ";
        }
    }
    // calls the recursive traverse

    void traverseBackward(LinkedList list) {
        if (list != NULL) {
            cout << "List (backward)[ ";
            traverse_recursive(list);
            cout << "]" << endl;
        } else {
            cout << "The list is empty" << endl;
        }
    }
    // a simple linear search to stop when
    // we find an occurrence of name in the list
    // returns it's index in the list
    // if not found returns -1

    int find(LinkedList list, char* name) {
        int count = 0;
        while (list != NULL) {
            if (str_compare(name, list->name) == 0)
                return count;
            else
                count++;
            list = list->next;
        }
        // if the list end reached
        // implies no occurrence of name was
        // found in the list
        if (list == NULL)
            return -1;
    }
}

int main() {
    cout << "Where do you want to store names ?" << endl;
    cout << "1. Array list " << endl;
    cout << "2. Linked list" << endl;
    char optionI, optionII;
    char *name;
    int p, index;
    bool loop = true;
    PartA::List arrayList;
    PartA::init(arrayList);
    PartB::LinkedList linkedList;
    PartB::init(linkedList);
    cout << "option: ";
    cin >> optionI;
    cout << "1. insert new item" << endl;
    cout << "2. delete an item" << endl;
    cout << "3. find an item" << endl;
    cout << "4. print the list in increasing order" << endl;
    cout << "5. print the list in decreasing order" << endl;
    cout << "q. to exit" << endl;
    while (loop) {
        cout << "Select option: ";
        cin >> optionII;
        cin.ignore();
        name = new char[10];
        if (optionI == '1') {
            switch (optionII) {
                case '1':
                    cout << "Enter name: ";
                    cin.getline(name, 10);
                    cout << "Enter position: ";
                    cin >> p;
                    PartA::insert(arrayList, p, name);
                    break;
                case '2':
                    cout << "Enter position: ";
                    cin >> p;
                    PartA::remove(arrayList, p);
                    break;
                case '3':
                    cout << "Enter name to find: ";
                    cin.getline(name, 10);
                    index = PartA::find(arrayList, name);
                    if (index != -1) {
                        cout << "name found at: " << index << endl;
                    } else {
                        cout << "name not found" << endl;
                    }
                    break;
                case '4':
                    PartA::traverseForward(arrayList);
                    break;
                case '5':
                    PartA::traverseBackward(arrayList);
                    break;
                case 'q':
                    loop = false;
                    break;
            }
        } else {
            switch (optionII) {
                case '1':
                    cout << "Enter name: ";
                    cin.getline(name, 10);
                    cout << "Enter position: ";
                    cin >> p;
                    PartB::insert(linkedList, p, name);
                    break;
                case '2':
                    cout << "Enter position: ";
                    cin >> p;
                    PartB::remove(linkedList, p);
                    break;
                case '3':
                    cout << "Enter name to find: ";
                    cin.getline(name, 10);
                    index = PartB::find(linkedList, name);
                    if (index != -1) {
                        cout << "name found at: " << index << endl;
                    } else {
                        cout << "name not found" << endl;
                    }
                    break;
                case '4':
                    PartB::traverseForward(linkedList);
                    break;
                case '5':
                    PartB::traverseBackward(linkedList);
                    break;
                case 'q':
                    loop = false;
                    break;
            }
        }
        cout << "------------------------" << endl;
    }
    return 0;
}