More than one duplicated element in C

Let’s say I have an array like this:

int array[]={1, 2, 2, 1, 2, 4, 4, 5};

I want to display all duplicate elements only once, display their corresponding frequency and count total duplicate elements. I searched about it a lot but every solution is for an array that has only 2 duplicate elements.

void non_unique_numbers(int arr[], int size){
    int i,j;
    int frequency[Frequency_size]={0};
    for(i=0; i<size; i++){
        for(j=0; j<size; j++){
            if(arr[i]==arr[j] && i!=j){
                ++frequency[arr[j]];
                printf("Number: %d  , Frequency: %d\n", arr[j], frequency[j]);
            }
        }
    }
}

When I run this my output is:

Number: 1  , Frequency: 3
Number: 2  , Frequency: 1
Number: 2  , Frequency: 1
Number: 2  , Frequency: 1
Number: 2  , Frequency: 2
Number: 1  , Frequency: 0
Number: 2  , Frequency: 2
Number: 2  , Frequency: 6
Number: 4  , Frequency: 0

which is meaningless. How can I display every duplicate element once and find out their corresponding frequency?

>Solution :

Rather than nested loops, you need two loops.

One to calculate the frequency. And, another that displays the frequencies and calculates the total number of duplicate numbers.

Here is the refactored code:

#include <stdio.h>

#define Frequency_size      10000

void
non_unique_numbers(int arr[], int size)
{
    int i;
    int freq;
    int totdup = 0;

    int frequency[Frequency_size] = { 0 };

    // calculate frequency
    for (i = 0; i < size; i++)
        ++frequency[arr[i]];

    for (i = 0; i < size; i++) {
        freq = frequency[arr[i]];
        printf("Number: %d  , Frequency: %d\n", arr[i], freq);
        if (freq >= 2)
            ++totdup;
    }

    printf("The number of duplicated numbers is: %d\n",totdup);
}

UPDATE:

Yes but it still displays the same element more than once –
goku

Oops, my bad … Here is one that indexes into the frequency table on the second loop:

#include <stdio.h>

#define Frequency_size      10000

void
non_unique_numbers(int arr[], int size)
{
    int i;
    int freq;
    int totdup = 0;

    int frequency[Frequency_size] = { 0 };

    // calculate freqency
    for (i = 0; i < size; i++)
        ++frequency[arr[i]];

    for (i = 0; i < Frequency_size; i++) {
        freq = frequency[i];
        if (freq <= 0)
            continue;

        printf("Number: %d  , Frequency: %d\n", i, freq);

        if (freq >= 2)
            ++totdup;
    }

    printf("The number of duplicated numbers is: %d\n",totdup);
}