Program Explanation

This C program counts the frequencies of elements in an integer array using a hash table (implemented as an array). The program uses a simple approach to hash the elements by using their values as indices in a frequency array. It assumes that the elements are non-negative integers.

Program Structure

• Include Headers: Necessary header files are included for standard input/output.
• Define Constants: A constant for the maximum size of the frequency array.
• Main Function: Contains the logic to input the array, count frequencies, and display results.
• Frequency Counting: A loop iterates through the input array, updating the frequency array based on the element values.
• Output: Finally, the program outputs the frequencies of each element present in the input array.

Code

#include 

#define MAX 1000 // Maximum value of elements in the array

int main() {
    int arr[MAX], freq[MAX] = {0}; // Initialize frequency array to 0
    int n, i;

    // Input size of the array
    printf("Enter the number of elements in the array: ");
    scanf("%d", &n);

    // Input elements of the array
    printf("Enter %d elements:\n", n);
    for (i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }

    // Count frequencies
    for (i = 0; i < n; i++) {
        freq[arr[i]]++; // Increment frequency of the element
    }

    // Display frequencies
    printf("Element\tFrequency\n");
    for (i = 0; i < MAX; i++) { if (freq[i] > 0) {
            printf("%d\t%d\n", i, freq[i]);
        }
    }

    return 0;
}

How to Compile and Run

1. Open a terminal or command prompt.
2. Copy the code into a file named frequency_count.c.
3. Compile the program using gcc frequency_count.c -o frequency_count.
4. Run the program using ./frequency_count.

Example

Input:

Enter the number of elements in the array: 7
Enter 7 elements:
1 2 3 2 1 1 4

Output:

Element	Frequency
1	3
2	2
3	1
4	1

Conclusion

This program demonstrates how to efficiently count the frequencies of elements in an array using hashing. The use of a frequency array allows for constant-time complexity for frequency counting, making it suitable for large datasets with known bounds on element values.