我对编程很陌生。有没有办法把这个If else语句改成一个循环，把这个书的列表按升序和降序或者（每个主题的书）的数量排序。
基本上，它模拟了一个图书馆系统，在那里你选择一个主题，然后你会看到未排序的书籍与数量之前的书籍名称，最后你会选择你想如何看到列表无论是升序或降序列表。

#include<iostream>
using namespace std;

int main()
{
    int subject;
    cout<<"What subject? \n" ;
    cout<<"[1] English \n" ;
    cout<<"[2] Mathematics \n" ;
    cout<<"[3] Science \n" ;
    cout<<"[4] Filipino \n\n" ;
    cin>>subject;
    switch(subject) {
        case 1 : cout<<"How do you want to see the books on this subject? \n\n";
                 cout<<"3 Spelling\n" ;
                 cout<<"5 Alphabet\n" ;
                 cout<<"6 Punctuations\n" ;
                 cout<<"2 Grammar\n" ;
                 cout<<"5 Alphabet\n" ;
                 cout<<"1 Literature\n\n" ;
        {

        int a = 1;
        int ans;

        ans=a;

        int inp;
        cout<<"type 1 for ascending and 2 for descending\n \n"<<endl;
        cin>>inp;

        if (inp==ans) {
        cout<<"Ascending\n\n" ;
        cout<<"1 Literature\n" ;
        cout<<"2 Grammar\n" ;
        cout<<"3 Spelling\n" ;
        cout<<"4 Short Stories\n" ;
        cout<<"5 Alphabet\n" ;
        cout<<"6 Punctuations\n" ;}
        else{
        cout<<"Descending\n\n" ;
        cout<<"6 Punctuations \n" ;
        cout<<"5 Alphabet \n" ;
        cout<<"4 Short Stories \n" ;
        cout<<"3 Spelling \n" ;
        cout<<"2 Grammar\n" ;
        cout<<"1 Literature\n" ;
       
         } 
         } 
        break;
        case 2 : cout<<"How do you want to see the books on this subject? \n";
                 cout<<"3 Calculus\n" ;
                 cout<<"1 Algebra\n" ;
                 cout<<"6 Trigonometry\n" ;
                 cout<<"4 Graphs\n" ;
                 cout<<"2 Functiosn\n" ;
                 cout<<"5 Geometry\n\n" ;
        {

        int a = 1;
        int ans;

        ans=a;

        int inp;
        cout<<"type 1 for ascending and 2 for descending\n \n"<<endl;
        cin>>inp;

        if (inp==ans) {
        cout<<"Ascending\n\n" ;
        cout<<"1 Algebra\n" ;
        cout<<"2 Functiosn\n" ;
        cout<<"3 Calculus\n" ;
        cout<<"4 Graphs\n" ;
        cout<<"5 Geometry\n" ;
        cout<<"6 Trigonometry\n" ;}
        else{
        cout<<"Descending\n\n" ;
        cout<<"6 Trigonometry \n" ;
        cout<<"5 Geometry \n" ;
        cout<<"4 Graphs \n" ;
        cout<<"3 Calculus \n" ;
        cout<<"2 Functions \n" ;
        cout<<"1 Algebra \n" ;
       
         } 
         }
        break;
        case 3 : cout<<"How do you want to see the books on this subject? \n";
                 cout<<"3 Solar system\n" ;
                 cout<<"1 Living things\n" ;
                 cout<<"6 Newton's Theory\n" ;
                 cout<<"4 Energy\n" ;
                 cout<<"2 Non-living things\n" ;
                 cout<<"5 Elements\n\n" ;
        {

        int a = 1;
        int ans;

        ans=a;

        int inp;
        cout<<"type 1 for ascending and 2 for descending\n \n"<<endl;
        cin>>inp;

        if (inp==ans) {
        cout<<"Ascending\n\n" ;
        cout<<"1 Living things\n" ;
        cout<<"2 Non-living things\n" ;
        cout<<"3 Solar system\n" ;
        cout<<"4 Energy\n" ;
        cout<<"5 Elements\n" ;
        cout<<"6 Newton's Theory\n" ;}
        else{
        cout<<"Descending\n\n" ;
        cout<<"6 Newton's Theory\n" ;
        cout<<"5 Elements \n" ;
        cout<<"4 Energy \n" ;
        cout<<"3 Solar system \n" ;
        cout<<"2 Non-living things\n" ;
        cout<<"1 Living things\n" ;
       
         } 
         }
        break;
        case 4 : cout<<"How do you want to see the books on this subject? \n";
                 cout<<"3 Gramatika\n" ;
                 cout<<"1 Pandiwa\n" ;
                 cout<<"6 Tamang Pagbigkas\n" ;
                 cout<<"4 Bantas\n" ;
                 cout<<"5 Mga kilalang manunulat\n" ;
                 cout<<"2 Maikling Kwento\n\n" ;
        {

        int a = 1;
        int ans;

        ans=a;

        int inp;
        cout<<"type 1 for ascending and 2 for descending\n \n"<<endl;
        cin>>inp;

        if (inp==ans) {
        cout<<"Ascending\n\n" ;
        cout<<"1 Pandiwa\n" ;
        cout<<"2 Maikling Kwento\n" ;
        cout<<"3 Gramatika\n" ;
        cout<<"4 Bantas\n" ;
        cout<<"5 Mga kilalang manunulat\n" ;
        cout<<"6 Tamang Pagbigkas\n" ;}
        else{
        cout<<"Descending\n\n" ;
        cout<<"6 Tamang Pagbigkas \n" ;
        cout<<"5 Mga kilalang manunulat \n" ;
        cout<<"4 Bantas \n" ;
        cout<<"3 Gramatika \n" ;
        cout<<"2 Maikling kwento\n" ;
        cout<<"1 Pandiwa\n" ;
       
         } 
         }
        break; 
        default : cout<<"Choose between 1,2,3,and 4";
        }
    
}