C program to find the frequency of each element in the array

2. C program to find the frequency of each element in the array

In this program, we have an array of elements to count the occurrence of its each element. One of the approaches to resolve this problem is to maintain one array to store the counts of each element of the array. Loop through the array and count the occurrence of each element as frequency and store it in another array fr.

In the given array, 1 has appeared two times so its frequency be 2 and 2 has appeared four times so have frequency 4 and so on.

ALGORITHM:

STEP 1: START
STEP 2: INITIALIZE arr[] ={1, 2, 8, 3, 2, 2, 2, 5, 1 }.
STEP 3: length = sizeof(arr)/sizeof(arr[0])
STEP 4: DEFINE fr[length].
STEP 5: SET visited = -1.li>
STEP 6: SET i= 0. REPEAT STEP 7 to STEP 12 UNTIL i<length.
STEP 7: SET count = 1
STEP 8: SET j =0. REPEAT STEP 9 and STEP 10 UNTIL j<length.
STEP 9: if(arr[i]==arr[j]) then
count++
fr[j] =visited
STEP 10: j= j+1.
STEP 11: if(fr[i]!=visited) then
fr[i]=count
STEP 12: i=i+1
STEP 13: PRINT "------------"
STEP 14: PRINT "Element | Frequency"
STEP 15: PRINT "-------------"
STEP 16: SET i=0. REPEAT STEP 17 to STEP 18 UNTIL i<length.
STEP 17: if(fr[i]!=visited) then
PRINT arr[i]
PRINT | PRINT fr[i]
STEP 18: i=i+1.
STEP 19: PRINT "-------------"
STEP 20: RETURN 0.
STEP 21: END

PROGRAM:

#include <stdio.h>  
   
int main()  
{  
    //Initialize array   
    int arr[] = {1, 2, 8, 3, 2, 2, 2, 5, 1};   
      
    //Calculate length of array arr  
    int length = sizeof(arr)/sizeof(arr[0]);  
      
    //Array fr will store frequencies of element  
    int fr[length];  
    int visited = -1;  
      
    for(int i = 0; i < length; i++){  
        int count = 1;  
        for(int j = i+1; j < length; j++){  
            if(arr[i] == arr[j]){  
                count++;  
                //To avoid counting same element again  
                fr[j] = visited;  
            }  
        }  
        if(fr[i] != visited)  
            fr[i] = count;  
    }  
      
    //Displays the frequency of each element present in array  
    printf("---------------------\n");  
    printf(" Element | Frequency\n");  
    printf("---------------------\n");  
    for(int i = 0; i < length; i++){  
        if(fr[i] != visited){  
            printf("    %d", arr[i]);  
            printf("    |  ");  
            printf("  %d\n", fr[i]);  
        }  
    }  
    printf("---------------------\n");  
    return 0;  
}  

Output:

----------------------------------------
Element | Frequency
----------------------------------------
1           |         2
2           |         4
8           |         1
3           |         1
5           |         1
----------------------------------------

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