Quan ly sinh vien _ LinkedList

#include<bits/stdc++.h>
using namespace std;

struct sinhvien {
    string name ;
    int age ;
    double gpa ;
};

struct Node {
    sinhvien s ;
    Node* next ;
};

#define node Node*

int size (node head){
    int ans =0 ;
    while (head!= NULL ){
        ans++ ;
        head= head-> next ;
    }
    return ans ;
}


node makeNode (){
    sinhvien s ;
    cin.ignore();
    cout<<"Nhap ten sinh vien "<<endl;
    getline ( cin ,s.name );

    cout<<"Nhap tuoi : "<<endl;
    cin >> s.age;
    cout<<"Nhap gpa : "<<endl;
    cin >> s.gpa;
    node tmp = NULL;
    tmp = new Node ();
    tmp->s=s ;
    tmp->next= NULL;
    return tmp ;
}

void addFirst (node & head  ){
    node tmp = makeNode();
    if ( head == NULL ){
        head= tmp ;
        return ;
    }
    tmp->next = head;
    head= tmp;

}

void addLast (node& head){
    node tmp = makeNode();
    if ( head== NULL){
        head= tmp;
        return ;
    }
    node p= head ;
    while ( p->next != NULL  ){
        p=p->next ;

    }
    p->next = tmp;
}

void addMiddle ( node& head , int pos ){
    int n= size(head);

    if (head == NULL){
        node tmp = makeNode();
        head=tmp;
        return ;
    }
    if ( pos <=0 || pos > n+1   ){
        return ;
    }
    else if ( pos == 1 ){
        addFirst (head);

    }
    else if (pos== n+1 ){
        addLast(head);
    }
    else {
        node tmp = makeNode();
        node p= head;
        for (int i=1;i<pos-1;i++){
            p=p->next;
        }
        tmp->next = p->next ;
        p-> next = tmp;
    }
}


void inSV(sinhvien s ){
    cout<<"--------------------------"<<endl;
    cout<< "Ho ten sinh vien "<<s.name <<endl;
    cout<<"Tuoi sinh vien : "<< s.age <<endl;
    cout<<"Gpa : "<<s.gpa <<endl;
    cout<<"--------------------------"<<endl;
}


void inDSLK(node head ){
    while ( head!= NULL ){
        // insv
        inSV(head->s);
        head=head->next ;
    }
}


void removeFirst (node & head){
    head= head->next ;
}
void removeLast( node & head)
{
    node p = head ;
    node truoc  = p;
    while ( p->next != NULL ){
        truoc  = p;
        p=p->next ;
    }
    truoc->next = NULL;
}

void removeMiddle (node & head, int pos ){
    int n= size(head);
    if ( head == NULL) return ;
    if ( pos == 1 ) {
        removeFirst(head);
    }
    else if ( pos == n ) {
        removeLast(head);
    }
    else {
        node p = head;
        for (int i=1;i<pos-1;i++){
            p=p->next ;
        }
        p->next= (p->next)->next ;
    }
}

void sapXep (node & head ){
    for (node p= head;p->next!=NULL;p=p->next ){
        node q= p;
        for (node m = q ; m->next!=NULL;m=m->next ){
            if ( q->s.gpa > m->s.gpa   ){
                q=m;
            }
        }
        sinhvien tmp  = p->s ;
        p->s=q->s;
        q->s= tmp;

    }
}

int main(){
    node head= NULL;
    // dslk ban dau la rong (null)
    while ( 1 ){
        for (int i=1;i<=50;i++){
            cout<<"                                           "<<endl;
        }
        cout<<"---------------------------------"<<endl;
        cout <<"1.Them SV vao dau danh sach "<<endl;
        cout<<"2.Them SV vao cuoi danh sach "<<endl;
        cout<<"3.Them SV vao giua danh sach "<<endl;
        cout<<"4.Xoa SV o dau danh sach "<<endl;
        cout<<"5.Xoa SV o cuoi danh sach "<<endl;
        cout<<"6.Xoa SV o giua danh sach "<<endl;
        cout<<"7.In DSLK "<<endl;
        cout<<"8.Thoat "<<endl;
        cout<<"9.Sap xep theo GPA "<<endl;
        cout<<"Nhap lua chon "<<endl;

        cout<<"---------------------------------"<<endl;

        int lc ;
        cin >> lc ;

        if ( lc== 1) {
            addFirst (head);
        }
        else if (lc == 2 ){
            addLast(head);
        }
        else if ( lc== 3 ){
            int pos ;
            cout<<"Nhap vi tri can them "<<endl;
            cin.ignore();
            cin >> pos ;
            addMiddle(head,pos);
        }
        else if ( lc == 4 ){
                 removeFirst ( head) ;
        }
        else if ( lc == 5 ){
            removeLast(head);
        }
        else if ( lc==6 ){
            int pos ;
            cout<<"Nhap vi tri can xoa "<<endl;
            cin >> pos ;
            removeMiddle(head,pos );
        }
        else if ( lc==7) {
            inDSLK(head);
        }
        else if ( lc == 8 ){
            break;
        }
        else if ( lc == 9){
            sapXep(head);
        }
    }

    return 0;
}