Fibonacci Number Program Problem

wutske

Jan 22 2006, 10:25 AM

I (finaly) started learning C. I'm using a book to learn it combined with some trial and error.
Now I've made a program to calculate the Fibonacci numbers, but there seems to be some error.

This is the source code:

CODE

#include <stdio.h>

main()
{
int fib1, fib2, fib, i, inp;

printf("************************************************");
printf("\n* Welcome to the Fibonacci Number Program v0.1 *\n");
printf("************************************************");
printf("\nWich Fibonacci Number do you want?\n");
scanf("%d", &inp);
fib1 = 1;
fib2 = 0;
switch(inp)
{
case 0:
printf("\n Sorry, no result for f(0)");
break;
case 1:
printf("\n Fib(1) = 0");
break;
case 2:
printf("\n Fib(1) = 0");
printf("\n Fib(2) = 1");
break;
default:
printf("\n Fib(1) = 0");
printf("\n Fib(2) = 1");
for (i=1; i<= inp -2; ++i)
{
fib = fib1 + fib2;
fib2 = fib1;
fib1 = fib;
printf("\n Fib(%d) = %d", i + 2, fib);
}
}
}

and this is the output for 55:

CODE

************************************************
* Welcome to the Fibonacci Number Program v0.1 *
************************************************
Wich Fibonacci Number do you want?

Fib(1) = 0
Fib(2) = 1
Fib(3) = 1
Fib(4) = 2
Fib(5) = 3
Fib(6) = 5
Fib(7) = 8
Fib(8) = 13
Fib(9) = 21
Fib(10) = 34
Fib(11) = 55
Fib(12) = 89
Fib(13) = 144
Fib(14) = 233
Fib(15) = 377
Fib(16) = 610
Fib(17) = 987
Fib(18) = 1597
Fib(19) = 2584
Fib(20) = 4181
Fib(21) = 6765
Fib(22) = 10946
Fib(23) = 17711
Fib(24) = 28657
Fib(25) = 46368
Fib(26) = 75025
Fib(27) = 121393
Fib(28) = 196418
Fib(29) = 317811
Fib(30) = 514229
Fib(31) = 832040
Fib(32) = 1346269
Fib(33) = 2178309
Fib(34) = 3524578
Fib(35) = 5702887
Fib(36) = 9227465
Fib(37) = 14930352
Fib(38) = 24157817
Fib(39) = 39088169
Fib(40) = 63245986
Fib(41) = 102334155
Fib(42) = 165580141
Fib(43) = 267914296
Fib(44) = 433494437
Fib(45) = 701408733
Fib(46) = 1134903170
Fib(47) = 1836311903
Fib(48) = -1323752223
Fib(49) = 512559680
Fib(50) = -811192543
Fib(51) = -298632863
Fib(52) = -1109825406
Fib(53) = -1408458269
Fib(54) = 1776683621
Fib(55) = 368225352

So something goes wrong at Fib(47), but I don't know what

I've mainly used this information to make the program.

Ow, and any tips to improve my code are always welcome

wutske

Jan 22 2006, 12:06 PM

I suddenly realised that an int is limited in size, so I changed the fibs to float and the problem is solved.
New code:

CODE

#include <stdio.h>

main()
{
int i, inp;
float fib1, fib2, fib;

printf("************************************************");
printf("\n* Welcome to the Fibonacci Number Program v0.1 *\n");
printf("************************************************");
printf("\nWich Fibonacci Number do you want?\n");
scanf("%d", &inp);
fib1 = 1;
fib2 = 0;
switch(inp)
{
case 0:
printf("\n Sorry, no result for f(0)");
break;
case 1:
printf("\n Fib(1) = 0");
break;
case 2:
printf("\n Fib(1) = 0");
printf("\n Fib(2) = 1");
break;
default:
printf("\n Fib(1) = 0");
printf("\n Fib(2) = 1");
for (i=3; i<= inp; ++i)
{
fib = fib1 + fib2;
fib2 = fib1;
fib1 = fib;
printf("\n Fib(%d) = %.0f", i, fib);
}
}
}

The new output is now:

CODE

************************************************
* Welcome to the Fibonacci Number Program v0.1 *
************************************************
Wich Fibonacci Number do you want?

Fib(1) = 0
Fib(2) = 1
Fib(3) = 1
Fib(4) = 2
Fib(5) = 3
Fib(6) = 5
Fib(7) = 8
Fib(8) = 13
Fib(9) = 21
Fib(10) = 34
Fib(11) = 55
Fib(12) = 89
Fib(13) = 144
Fib(14) = 233
Fib(15) = 377
Fib(16) = 610
Fib(17) = 987
Fib(18) = 1597
Fib(19) = 2584
Fib(20) = 4181
Fib(21) = 6765
Fib(22) = 10946
Fib(23) = 17711
Fib(24) = 28657
Fib(25) = 46368
Fib(26) = 75025
Fib(27) = 121393
Fib(28) = 196418
Fib(29) = 317811
Fib(30) = 514229
Fib(31) = 832040
Fib(32) = 1346269
Fib(33) = 2178309
Fib(34) = 3524578
Fib(35) = 5702887
Fib(36) = 9227465
Fib(37) = 14930352
Fib(38) = 24157816
Fib(39) = 39088168
Fib(40) = 63245984
Fib(41) = 102334152
Fib(42) = 165580128
Fib(43) = 267914272
Fib(44) = 433494400
Fib(45) = 701408640
Fib(46) = 1134903040
Fib(47) = 1836311680
Fib(48) = 2971214848
Fib(49) = 4807526400
Fib(50) = 7778741248
Fib(51) = 12586267648
Fib(52) = 20365008896
Fib(53) = 32951275520
Fib(54) = 53316284416
Fib(55) = 86267559936

Vyoma

Feb 13 2006, 07:36 PM

I am not sure about it, but float may result in rounding off errors (May not pertain to this particular example).

Try using 'long' and see if you get the same result.

twitch

Feb 14 2006, 10:13 AM

You could always comment your coding throughout, that way it is easier to refer to it later on.

Unitechy

May 28 2006, 12:46 PM

Well firstly i'm considering fibonacii series starting with 1 1

there are two types starting with 0 and starting with 1 i am sure you know this.

Secondly why 're you taking switch its tedious..

This is simple and easy to understand

CODE

#include <stdio.h>
void main()
{
  int a=1,b=1,c,x;
    printf("Enter the number for which fibonacii to be found");
    scanf("%d",&n);
    printf("%d \n %d \n,a,b);
    for(x=1;x<=n-2;x++);
    { c=a+b;
     printf("%d\n",c);
     a=b;
     b=c;
    }
}

i hope this helped.
Btw don't shout on me if it didn't cause even i am new learner lol

QUOTE(Vyoma @ Feb 13 2006, 08:36 AM)

I am not sure about it, but float may result in rounding off errors (May not pertain to this particular example).

Try using 'long' and see if you get the same result.

abhishek

Jun 18 2006, 09:03 PM

Try using sizeof() function to determine the size of int and long. This will be different in different systems. Sometimes the size of long will be equal to that of int and sometimes small will be equal to int. The last number is 5bytes long so the size of long should be greater than 5 if you will use long.

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Fibonacci Number Program Problem - n00b :)

Fibonacci Number Program Problem - n00b :)