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:

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// 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;
}

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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++















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// 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; 


} 



















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Python3














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# 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 



















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<?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 


?> 



















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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






          
          
          
          

            

    

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