fibonacci.c File Reference

Program to print the nth term of the Fibonacci series. More...

#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

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Functions
unsigned int	fib (int number)
	for assert() for errno - to determine whether there is an error while using strtol()
int	getInput (void)
	Get the input from the user.
static void	test ()
	self-test implementation
int	main ()
	Main function.

Detailed Description

Program to print the nth term of the Fibonacci series.

Fibonacci series generally starts from 0 and 1. Every next term in the series is equal to the sum of the two preceding terms. For further info: https://en.wikipedia.org/wiki/Fibonacci_sequence

Author

Luiz Carlos Aguiar C

Niranjan

Function Documentation

fib()

unsigned int fib

(

int

number

)

for assert() for errno - to determine whether there is an error while using strtol()

for input, output for exit() - to exit the program to calculate time taken by fib()

Determines the nth Fibonacci term

Parameters

number

- n in "nth term" and it can't be negative as well as zero

Returns

nth term in unsigned type

Warning

Only till 47th and 48th fibonacci element can be stored in int and unsigned int respectively (takes more than 20 seconds to print)

{
    // Check for negative integers
    if (number <= 0)
    {
        fprintf(stderr, "Illegal Argument Is Passed!\n");
        exit(EXIT_FAILURE);
    }
 
    // Base conditions
    if (number == 1)
        return 0;
 
    if (number == 2)
        return 1;
 
    // Recursive call to the function
    return fib(number - 1) + fib(number - 2);
}

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getInput()

int getInput

(

void

)

Get the input from the user.

Returns

valid argument to the fibonacci function

{
    int num, excess_len;
    char buffer[3], *endPtr;
 
    while (1)
    {  // Repeat until a valid number is entered
        printf("Please enter a valid number:");
        fgets(buffer, 3, stdin);  // Inputs the value from user
 
        excess_len = 0;
        if (!(buffer[0] == '\n' ||
            buffer[1] == '\n' ||
            buffer[2] == '\n')) {
            while (getchar() != '\n') excess_len++;
        }
 
        num = strtol(buffer, &endPtr,
                     10);  // Attempts to convert the string to integer
 
        // Checking the input
        if (  // The number is too large
            (excess_len > 0 || num > 48) ||
            // Characters other than digits are included in the input
            (*endPtr != '\0' && *endPtr != '\n') ||
            // No characters are entered
            endPtr == buffer)
        {
            continue;
        }
 
        break;
    }
 
    printf("\nEntered digit: %d (it might take sometime)\n", num);
    return num;
}

main()

int main

(

void

)

Main function.

Returns

0 on exit

{
    // Performing the test
    test();
    printf("Tests passed...\n");
 
    // Getting n
    printf(
        "Enter n to find nth fibonacci element...\n"
        "Note: You would be asked to enter input until valid number ( less "
        "than or equal to 48 ) is entered.\n");
 
    int number = getInput();
    clock_t start, end;
 
    start = clock();
    printf("Fibonacci element %d is %u ", number, fib(number));
    end = clock();
 
    printf("in %.3f seconds.\n", ((double)(end - start)) / CLOCKS_PER_SEC );
    return 0;
}

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test()

static void test ( void  )

static

self-test implementation

Returns

void

{
    assert(fib(5) == 3);
    assert(fib(2) == 1);
    assert(fib(9) == 21);
}

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