Print numbers in descending order along with their frequencies

Given an array arr, the task is to print the elements of the array in descending order along with their frequencies.

Examples:

Input: arr[] = {1, 3, 3, 3, 4, 4, 5}
Output: 5 occurs 1 times
4 occurs 2 times
3 occurs 3 times
1 occurs 1 times

Input: arr[] = {1, 1, 1, 2, 3, 4, 9, 9, 10}
Output: 10 occurs 1 times
9 occurs 2 times
4 occurs 1 times
3 occurs 1 times
2 occurs 1 times
1 occurs 3 times



Naive approach: Use some Data-Structure (e.g. multiset) which stores elements in decreasing order and then print the elements one by one with it’s count and then erase it from the Data-structure. The time complexity will be O(N log N) and the auxiliary space will be O(N) for the Data-structure used.

Below is the implementation of the above approach:

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ program to print the elements in
// descending along with their frequencies
#include <bits/stdc++.h>
using namespace std;
  
// Function to print the elements in descending
// along with their frequencies
void printElements(int a[], int n)
{
  
    // A multiset to store elements in decreasing order
    multiset<int, greater<int> > ms;
  
    // Insert elements in the multiset
    for (int i = 0; i < n; i++) {
        ms.insert(a[i]);
    }
  
    // Print the elements along with their frequencies
    while (!ms.empty()) {
  
        // Find the maximum element
        int maxel = *ms.begin();
  
        // Number of times it occurs
        int times = ms.count(maxel);
  
        cout << maxel << " occurs " << times << " times\n";
  
        // Erase the maxel
        ms.erase(maxel);
    }
}
  
// Driver Code
int main()
{
    int a[] = { 1, 1, 1, 2, 3, 4, 9, 9, 10 };
    int n = sizeof(a) / sizeof(a[0]);
    printElements(a, n);
    return 0;
}

chevron_right






                        filter_none









Output:


10 occurs 1 times
9 occurs 2 times
4 occurs 1 times
3 occurs 1 times
2 occurs 1 times
1 occurs 3 times





Efficient Approach: Sort the array in descending order and then start printing the elements from the beginning along with their frequencies.


Below is the implementation of the above approach:




C++















                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















// C++ program to print the elements in 


// descending along with their frequencies 


#include <bits/stdc++.h> 


using namespace std; 


  


// Function to print the elements in descending 


// along with their frequencies 


void printElements(int a[], int n) 


{ 


  


    // Sorts the element in decreasing order 


    sort(a, a + n, greater<int>()); 


    int cnt = 1; 


  


    // traverse the array elements 


    for (int i = 0; i < n - 1; i++) { 


  


        // Prints the number and count 


        if (a[i] != a[i + 1]) { 


            cout << a[i] << " occurs " << cnt << " times\n"; 


            cnt = 1; 


        } 


        else


            cnt += 1; 


    } 


  


    // Prints the last step 


    cout << a[n - 1] << " occurs " << cnt << " times\n"; 


} 


  


// Driver Code 


int main() 


{ 


    int a[] = { 1, 1, 1, 2, 3, 4, 9, 9, 10 }; 


    int n = sizeof(a) / sizeof(a[0]); 


  


    printElements(a, n); 


    return 0; 


} 



















                        chevron_right







                        filter_none









Python3














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















# Python3 program to print the elements in  


# descending along with their frequencies  


  


# Function to print the elements in  


# descending along with their frequencies  


def printElements(a, n) : 


  


    # Sorts the element in decreasing order  


    a.sort(reverse = True)  


    cnt = 1


  


    # traverse the array elements  


    for i in range(n - 1) : 


  


        # Prints the number and count  


        if (a[i] != a[i + 1]) :  


            print(a[i], " occurs ", cnt, "times")  


            cnt = 1


          


        else : 


            cnt += 1


      


    # Prints the last step  


    print(a[n - 1], "occurs", cnt, "times")  


  


# Driver Code  


if __name__ == "__main__" : 


  


    a = [ 1, 1, 1, 2,  


          3, 4, 9, 9, 10 ]  


    n = len(a) 


  


    printElements(a, n) 


      


# This code is contributed by Ryuga 



















                        chevron_right







                        filter_none









PHP














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















<?php 


// PHP program to print the elements in 


// descending along with their frequencies 


  


// Function to print the elements in  


// descending along with their frequencies 


function printElements(&$a, $n) 


{ 


  


    // Sorts the element in  


    // decreasing order 


    rsort($a); 


    $cnt = 1; 


  


    // traverse the array elements 


    for ($i = 0; $i < $n - 1; $i++)  


    { 


  


        // Prints the number and count 


        if ($a[$i] != $a[$i + 1])  


        { 


            echo ($a[$i]);  


            echo (" occurs " ); 


            echo $cnt ; 


            echo (" times\n"); 


            $cnt = 1; 


        } 


        else


            $cnt += 1; 


    } 


  


    // Prints the last step 


    echo ($a[$n - 1]);  


    echo (" occurs "); 


    echo $cnt; 


    echo (" times\n"); 


} 


  


// Driver Code 


$a = array(1, 1, 1, 2, 3, 


           4, 9, 9, 10 ); 


$n = sizeof($a); 


  


printElements($a, $n); 


  


// This code is contributed 


// by Shivi_Aggarwal 


?> 



















                        chevron_right







                        filter_none











Output:


10 occurs 1 times
9 occurs 2 times
4 occurs 1 times
3 occurs 1 times
2 occurs 1 times
1 occurs 3 times






          
          
          
          

            

    

        My Personal Notes
        arrow_drop_up
    

    

        
        

            
            
        

    


Recommended Posts:
Striver
Striver(underscore)79 at Codechef and codeforces D
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on  the "Improve Article" button below.


Improved By :  Ryuga, Shivi_Aggarwal