Lab 2 = Insert and Merge

#include<iostream>
using namespace std;

class student
{
public:
    int id;
    string name;
    int credit;
    float cgpa;

    void input()
    {
        cin>>id>>name>>credit>>cgpa;
    }
    void output()
    {
        cout<<"\t"<<id;
        cout<<"\t"<<name;
        cout<<"\t"<<credit;
        cout<<"\t"<<cgpa;
        cout<<endl;
    }
};

void insertion(student s[],int n)
{
    int i,j;
    student key;
    for(j=2; j<=n; j++)
    {
        key=s[j];
        i=j-1;
        while(i>0&&s[i].credit<=key.credit)
        {
            if(s[i].credit==key.credit)
            {
                if(s[i].cgpa<key.cgpa)
                {
                    s[i+1]=s[i];
                }
            }
            s[i+1]=s[i];
            i=i-1;
        }
        s[i+1]=key;
    }
}


void merge(student a[],int p,int q,int r)
{
    int n1,n2,i,j,k;
    student l[200];
    student m[200];
    n1=q-p+1;
    n2=r-q;
    for(i=1; i<=n1; i++)
    {
        l[i]=a[p+i-1];
    }
    for(j=1; j<=n2; j++)
    {
        m[j]=a[q+j];
    }
    l[n1+1].credit=-234154;
    m[n2+1].credit=-123555;
    i=1;
    j=1;
    for(k=p; k<=r; k++)
    {
        if(l[i].credit==m[j].credit)
        {
            if(l[i].cgpa>m[j].cgpa)
            {

                a[k]=l[i];
                i++;
            }
            else
            {
                a[k]=m[j];
                j++;
            }
        }

        else if(l[i].credit>m[j].credit)
        {

            a[k]=l[i];
            i++;
        }
        else
        {
            a[k]=m[j];
            j++;
        }
    }

}
void mergesort(student s[],int p,int r)
{
    int q;
    if(p<r)
    {
        q=(p+r)/2;
        mergesort(s,p,q);
        mergesort(s,q+1,r);
        merge(s,p,q,r);

    }
}

int main()
{
    ofstream myfile ("input.text");
    student s[100];
    int n,i,choice;

    cout<<"Enter the number of student:";
    cin>>n;
    cout<<"\nStudent information\n";
    for(i=1; i<=n; i++)
    {
        s[i].input();
    }
    cout<<"\n1. Insertion sort";
    cout<<"\n2. Merge sort";
    cout<<"\n3. Exit";
    while(1)
    {
        cout<<"\nEnter your choice:";
        cin>>choice;

        if(choice==1)
        {
            insertion(s,n);
        }
        else if(choice==2)
        {
            mergesort(s,1,n);
        }
        else if(choice==3)
        {
            break;
        }
        cout<<"\nStudent Sorted Information\n";
        for(i=1; i<=n; i++)
        {
            s[i].output();
        }
    }
    return 0;
}