Example: Fibonacci Series (Recursive) in C

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// Fibonacci Series (Recursive)
#include <stdio.h>

// Function to calculate the nth Fibonacci number
int fibonacci(int num) {
    if (num <= 1) {
        return num;
    } else {
        return fibonacci(num - 1) + fibonacci(num - 2);
    }
}

int main() {
    int n, i;

    // Step 1: Prompt user for the number of terms
    printf("Enter the number of terms: ");
    scanf("%d", &n);

    printf("Fibonacci Series: ");

    // Step 2: Handle invalid input
    if (n < 0) {
        printf("Please enter a non-negative integer.\n");
    } else {
        // Step 3: Loop and call the recursive function for each term
        for (i = 0; i < n; i++) {
            printf("%d", fibonacci(i));
            if (i < n - 1) { // Print comma for all except the last term
                printf(", ");
            }
        }
        printf("\n");
    }

    return 0;
}