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assignment-s-17.c

Problem Statement

Write a program to display the Fibonacci series (i) using recursion (ii) using iteration

Metadata

Property Detail
Author Amit Dutta amitdutta4255@gmail.com
Date 21 Dec 2025
License MIT License (See the LICENSE file for details)
Difficulty Beginner (index: 2 / 10)

Concepts

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  • Recursion
  • Sorting (possible)
  • Iteration

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Source Code

#include <stdio.h>

long long int fib_rec(int);
long long int fib_tail_rec(int, long long int, long long int);
void fib_rec_print(int);
void fib_ite_print(int);

int main()
{
    int n;
    printf("Enter the number of terms: ");
    scanf("%d", &n);
    fib_rec_print(n);
    fib_ite_print(n);
    return 0;
}

long long int fib_rec(int n)
{
    if (n == 0 || n == 1)
    {
        return n;
    }
    else
    {
        return fib_rec(n - 1) + fib_rec(n - 2);
    }
}

long long int fib_tail_rec(int n, long long int t1, long long int t2)
{
    if (n == 0)
    {
        return t1;
    }
    else if (n == 1)
    {
        return t2;
    }
    else
    {
        return fib_tail_rec(n - 1, t2, t1 + t2);
    }
}

void fib_rec_print(int n)
{
    int i;
    printf("\nFibonacci Series (Recursion):");
    for (i = 0; i < n; i++)
    {
        printf("  %lld", fib_rec(i));
    }
    printf("\nFibonacci Series (Tail-Recursion):");
    for (i = 0; i < n; i++)
    {
        printf("  %lld", fib_tail_rec(i, 0, 1));
    }
}

void fib_ite_print(int n)
{
    int i;
    long long int t1 = 0, t2 = 1, temp;
    printf("\nFibonacci Series (Iteration):");
    if (n > 0)
    {
        printf("  0");
    }
    if (n > 1)
    {
        printf("  1");
    }
    for (i = 2; i < n; i++)
    {
        printf("  %lld", t1 + t2);
        temp = t1;
        t1 = t2;
        t2 = temp + t2;
    }
}

Explanation

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    You are explaining a C programming code to a beginner.

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    - Only use the given code. Do NOT assume anything not present.

    - Do NOT add extra examples.

    - Keep explanation clear and short.

    - If something is unclear, say "Not clear from code".

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    FORMAT:

    [START]

    ## What it does

    (Explain the overall purpose in 1-2 sentences)

    ## Step-by-step

    (Explain how the code works in steps, simple language)

    ## Key Concepts

    (List concepts like loop, condition, function, etc.)

    ## Notes

    (Mention any limitations, errors, or assumptions)

    [END]

    CODE (assignment-s-17.c):

    #include <stdio.h>

    long long int fib_rec(int);
    long long int fib_tail_rec(int, long long int, long long int);
    void fib_rec_print(int);
    void fib_ite_print(int);

    int main()
    {
        int n;
        printf("Enter the number of terms: ");
        scanf("%d", &n);
        fib_rec_print(n);
        fib_ite_print(n);
        return 0;
    }

    long long int fib_rec(int n)
    {
        if (n == 0 || n == 1)
        {
            return n;
        }
        else
        {
            return fib_rec(n - 1) + fib_rec(n - 2);
        }
    }

    long long int fib_tail_rec(int n, long long int t1, long long int t2)
    {
        if (n == 0)
        {
            return t1;
        }
        else if (n == 1)
        {
            return t2;
        }
        else
        {
            return fib_tail_rec(n - 1, t2, t1 + t2);
        }
    }

    void fib_rec_print(int n)
    {
        int i;
        printf("\nFibonacci Series (Recursion):");
        for (i = 0; i < n; i++)
        {
            printf("  %lld", fib_rec(i));
        }
        printf("\nFibonacci Series (Tail-Recursion):");
        for (i = 0; i < n; i++)
        {
            printf("  %lld", fib_tail_rec(i, 0, 1));
        }
    }

    void fib_ite_print(int n)
    {
        int i;
        long long int t1 = 0, t2 = 1, temp;
        printf("\nFibonacci Series (Iteration):");
        if (n > 0)
        {
            printf("  0");
        }
        if (n > 1)
        {
            printf("  1");
        }
        for (i = 2; i < n; i++)
        {
            printf("  %lld", t1 + t2);
            temp = t1;
            t1 = t2;
            t2 = temp + t2;
        }
    }