data structures - homework

#include <iostream>
#include <string>
#include <fstream>
#include <stdlib.h>

using namespace std;

struct Li
{
    int value;
    Li* nextitem;



};

typedef struct Li Listitem;

struct iL
{
    int nofitems;
    Listitem* firstitem;
};

typedef struct  iL intList;

void additemtoback(intList* i, Listitem* l);

Listitem* createnewlistitem(int x)
{
    //Listitem* newitem = (Listitem*)new(sizeof(Listitem));
    Listitem* newitem = new Listitem[1];
    if (newitem == NULL)
    {
        cout<<"Error";

        exit(-1);
    }

    newitem->value=x;

    newitem->nextitem=NULL;

    return newitem;
}

intList* createnewlist()
{
    intList* newlist = new intList[1];
    if (newlist == NULL)
    {
        cout<<"ERror #2";

        exit(-1);
    }
    newlist->nofitems=0;
    newlist->firstitem=NULL;

    return newlist;

}

void additemtofront(intList* i, Listitem* l)
{
    if (i->nofitems==0)
    {
        i->firstitem=l;
        i->nofitems=1;
    }
    else
    {
        l->nextitem=i->firstitem;
        i->firstitem=l;
        i->nofitems++;
    }
}

void addonetoall(intList* i)
{
    if(i->nofitems==0)
    {
        cout<<"nothing to add";
    }

    Listitem* currentitem = i->firstitem;

    while(currentitem->nextitem != NULL)
    {
        currentitem->value+=1;
        currentitem = currentitem->nextitem;
    }

    currentitem->value+=1;
}

int swap(intList* i, int x, int y)
{
    int replaced = 0;

    if(i->nofitems==0)
    {
        cout<<"Nothing to replace!";
    }

    Listitem* currentitem = i->firstitem;

    while(currentitem->nextitem != NULL)
    {
        if(currentitem->value == x)
        {
            currentitem->value=y;
            currentitem=currentitem->nextitem;
            replaced++;
        }

        else
        {
            currentitem=currentitem->nextitem;
        }
    }

    if(currentitem->value == x)
    {
        currentitem->value=y;
        replaced++;
    }

    return replaced;
}

int addsum(intList* i)
{
    int sum = 0;

    if(i->nofitems==0)
    {
        return sum;
    }

    Listitem* currentitem = i->firstitem;

    while(currentitem->nextitem!=NULL)
    {
        sum+=currentitem->value;

        currentitem = currentitem->nextitem;
    }

    sum+=currentitem->value;

    return sum;

}

void deletefromfront(intList* i)
{
        if(i->nofitems==0)
    {
        cout<<"Stop trying to delete"<<endl;
        return;
    }

        if(i->nofitems==1)
    {
        Listitem* onlyitem=i->firstitem;

        delete(onlyitem);

        onlyitem=NULL;

        i->firstitem=NULL;

        i->nofitems=0;
    }

            else
    {
        Listitem* firstitem=i->firstitem;

        i->firstitem=firstitem->nextitem;

        delete(firstitem);

        firstitem=NULL;

        i->nofitems--;
    }
}

void deletefromback(intList* i)
{
    if(i->nofitems==0)
    {
        cout<<"Stop trying to delete"<<endl;
        return;
    }

    if(i->nofitems==1)
    {
        Listitem* onlyitem=i->firstitem;

        delete(onlyitem);

        onlyitem=NULL;

        i->firstitem=NULL;

        i->nofitems=0;
    }

    else
    {
        Listitem* currentitem=i->firstitem;

        Listitem* seconditem=currentitem->nextitem;

        while(seconditem->nextitem!=NULL)
        {
            currentitem=seconditem;

            seconditem=currentitem->nextitem;
        }

        delete(seconditem);

        seconditem=NULL;

        currentitem->nextitem=NULL;

        i->nofitems--;
    }


}

void deletelist(intList * i)
{
    while(i->nofitems>0)
    {
        deletefromfront(i);

    }

    delete(i);

    i=NULL;
}



void additemtoback(intList* i, Listitem* l)
{
    if (i->nofitems==0)
    {
        additemtofront(i,l);

        return;
    }

    Listitem* currentitem = i->firstitem;
    while(currentitem->nextitem!=NULL)
        currentitem=currentitem->nextitem;

    currentitem->nextitem=l;

    i->nofitems++;
}

void printList(intList* l)
{
    if (l==NULL)
    {
        cout<<" NO LIST\n";
        return;
    }

    if (l->nofitems==0)
    {
        cout<<"No items to print!\n";
        return;
    }

    cout<<l->nofitems<<",";


    Listitem* currentItem = l->firstitem;

    while(currentItem->nextitem!=NULL)
    {
        cout<<currentItem->value<<"->";
        currentItem=currentItem->nextitem;
    }

    cout<<currentItem->value<<endl;

}

int main()
{
    Listitem * newitem;
    int choice= 9;
    intList * mylist=NULL;
    int ivalue;

    int x=999;
    int y=666;



    while(choice!= 0)
    {

        cout<<"Choose what you want!: "<<endl;
        cout<<"\t 0. Press 0 to exit."<<endl;
        cout<<"\t 1. CreateList."<<endl;
        cout<<"\t 2. add item to front."<<endl;
        cout<<"\t 3. add item to back."<<endl;
        cout<<"\t 4. print list."<<endl;
        cout<<"\t 5. delete from back."<<endl;
        cout<<"\t 6. delete from front."<<endl;
        cout<<"\t 7. add all items in list: "<<endl;
        cout<<"\t 8. add 1 to all items."<<endl;
        cout<<"\t 9. replace \"x\" with \"y\": "<<endl;

        cin>>choice;

        switch(choice)
        {
            case 1:

                if(mylist!=NULL)
                    deletelist(mylist);

                mylist=createnewlist();
                break;

            case 2:
                if(mylist==NULL)
                    mylist=createnewlist();
                cout<<"Please enter a value: ";
                cin>>ivalue;
                newitem= createnewlistitem(ivalue);
                additemtofront(mylist, newitem);
                break;
            case 3:
                if(mylist==NULL)
                    mylist=createnewlist();
                cout<<"Please enter a value to add to back: ";
                cin>>ivalue;

                newitem = createnewlistitem(ivalue);
                additemtoback(mylist,newitem);
                break;
            case 4:
                if(mylist==NULL)
                    mylist=createnewlist();
                printList(mylist);
                break;
            case 5:
                if(mylist==NULL)
                    mylist=createnewlist();
                deletefromback(mylist);
                break;
            case 6:
                if(mylist==NULL)
                    mylist=createnewlist();
                deletefromfront(mylist);
                break;
            case 7:
                if(mylist==NULL)
                    mylist=createnewlist();
                ivalue=addsum(mylist);
                cout<<"There are "<<ivalue<<" items in list"<<endl;
                break;
            case 8:
                if(mylist==NULL)
                    cout<<"create a list first!";
                addonetoall(mylist);
                break;
            case 9:
                cout<<"Enter the value you want to find and replace: ";
                cin>>x;

                cout<<"Enter the value to replace it with: ";
                cin>>y;

                swap(mylist,x,y);
                break;



        }

    }

    cout<<"Deleting lists...";
    if(mylist!=NULL)
        deletelist(mylist);


    return 0;
}