Fibonacci Series In C

Fibonacci series is a mathematical sequence of numbers first created by Leonardo Fibonacci in 1202.Starting with 0 and 1 , each new number is sum of  the previous two.In mathematics terms Fn  is the Fibonacci sequence is defined by recurrence relation  Fn=Fn-1+Fn-2 .



Example :


Serial no       Fibonacci series

   1                         0
   2                         1
   3                     0+1=1
   4                     1+1=2
   5                     1+2=3
   6                     2+3=5
   7                     3+5=8
   9                     5+8=13
  10                    8+13=21


Fibonacci Series Program  In C   :

#include<stdio.h>
#include<conio.h>
#include<time.h>
long double fib(int);
main()
{
    long double f;
    long int t1,t2,t3,*t=NULL;
    int n,i;
    char ch;
    do{
        clrscr();
        printf("\n\t Enter n(1-60):");
        scanf("%d",&n);
        for(i=1;i<=n;i++)
        {
            t1=time(t);
            f=fib(i);
            t2=time(t);
            t3=t2-t1;
            printf("\tfib(%d)=%19.00Lf  time=%5ld  secs\n",i,f,t3);
        }
        printf("\n\t Continue (y/n):");
        ch=getch();
    }while(ch=='y'||ch=='Y');
}
long double fib (int n)
{
    if (n<2)
    return 1;
    else
    return fib(n-1)+fib(n-2);
}

Output : C program Fibonacci series calculate time of the each output number.

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