A program to print ascending and descending order of n numbers using user defined functions in C++

Question

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i do not know how to use the user defined functions for the program to run properly

What I have tried:

C++

#include <iostream>
using namespace std;
sort Ascending( ); 
sort Descending( ); 
int main(){
	int num[100],n;
int i,j,man;
cout<<"enter n for the numbers you want to sort"<<endl<<endl;
cin>>n;
	for(i=0;i<n;i++){		
			cout<<"enter number"<<endl;
	cin>>num[i];
	}
	for(i=0;i<n;i++){
		for(j=0;j<n;j++){
			if(num[i]<num[j]){
				man=num[i];
				num[i]=num[j];
				num[j]=man;
			}			
		}
	}
	cout<<"ascending "<<endl;
	for(i=0;i<n;i++){
	cout<<" "<<num[i]<<endl;;
	}
	for(i=0;i<n;i++){
		for(j=0;j<n;j++){
			if(num[i]>num[j]){
				man=num[i];
				num[i]=num[j];
				num[j]=man;
			}			
		}
	}
	cout<<" descending"<<endl;
	for(i=0;i<n;i++){
		cout<<" "<<num[i]<<endl;
}
return 0;
}

Posted 27-Oct-19 8:37am

Member 14636287

Updated 1-Aug-21 22:37pm

KarstenK

v2

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Comments

Richard MacCutchan 27-Oct-19 16:47pm

That is because you have put the sorting code inline in main. You need to move the sort routines into their own functions.

2 solutions

Solution 1

A "user defined function" is just a function that you declare, just as you declare main i #n the code you show.
In fact, you ALMOST show the prototypes for two functions immediately above main - so all you have to do is give them valid names and move the code for "sorting in ascending order" to one function, and "sorting in descending order" in another. You can then call them from main just by using the name of the function followed by brackets (with any parameter values inside the brackets if needed):

C++

void MyFunction();    //Prototype - lets you use it in main before the definition

void main()
   {
   ...
   MyFunction();
   ...
   }
void MyFunction()
   {
   // your code here
   }

Posted 27-Oct-19 10:54am

OriginalGriff

Comments

Richard MacCutchan 28-Oct-19 4:34am

If you put the complete function above main in the source then there is no need for prototypes. One of the most annoying features of C/C++ (IMHO).

OriginalGriff 28-Oct-19 4:43am

True - but since he has "almost prototypes" in there already, it makes sense to continue with them.

C compilers used to be slow enough without adding yet another pass just to pick up forward references :laugh:

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CPallini · Accepted Answer · 2019-10-27T22:53:00

Just write your sorting code in ad hoc functions. You should avoid C like arrays for such a task.
Try

C++

#include <iostream>
#include <vector>
#include <utility>
using namespace std;

void sort_ascending(vector<int> & v);
void sort_descending(vector <int> & v);

int main()
{

  size_t n;
  cout << "enter n for the numbers you want to sort" << endl;
  cin >> n;
  cout << endl;

  vector<int> v(n);

  for (size_t i =0; i < n; ++i)
  {
    cout << "enter number " << (i+1) << " of " << n << endl;
    cin >> v[i];
  }
  cout << "ascending:\n";
  sort_ascending( v);
  for (auto x : v)
    cout << x << "\n";

  cout << "descending:\n";
  sort_descending(v);
  for (auto x : v)
    cout << x << "\n";
}

void sort_ascending( vector<int> & v)
{
  for (size_t i=0; i < v.size()-1; ++i)
    for (size_t j= i+1; j < v.size(); ++j)
      if ( v[i] > v[j] ) swap(v[i], v[j]);
}

void sort_descending( vector<int> & v)
{
  for (size_t i=0; i < v.size()-1; ++i)
    for (size_t j= i+1; j < v.size(); ++j)
      if ( v[i] < v[j] ) swap(v[i], v[j]);
}

That's a possible implementation of an exercise. On the other hand, if you are writing production code, then discard your own (bubble!) implementation of sort and use the one provided by the C++ standard library instead.

C++

#include <iostream>
#include <algorithm>
#include <functional>
#include <vector>
using namespace std;

int main()
{
  size_t n;
  cout << "enter n for the numbers you want to sort" << endl;
  cin >> n;
  cout << endl;

  vector<int> v(n);

  for (size_t i =0; i < n; ++i)
  {
    cout << "enter number " << (i+1) << " of " << n << endl;
    cin >> v[i];
  }

  cout << "ascending:\n";
  sort(v.begin(), v.end());
  for (auto x : v)
    cout << x << "\n";

  cout << "descending:\n";
  sort(v.begin(), v.end(), std::greater<int>());
  for (auto x : v)
    cout << x << "\n"
}