Problem 25
Statement
The Fibonacci sequence is defined by the recurrence relation:
F(n) = F(n−1) + F(n−2), where F(1) = 1 and F(2) = 1.
Hence the first 12 terms will be:
F(1) = 1
F(2) = 1
F(3) = 2
F(4) = 3
F(5) = 5
F(6) = 8
F(7) = 13
F(8) = 21
F(9) = 34
F(10) = 55
F(11) = 89
F(12) = 144
The 12th term, F(12), is the first term to contain three digits.
What is the first term in the Fibonacci sequence to contain 1000 digits?
Solution
The code, in C.
#include <stdio.h>
#define DIGIT 1000
int fibDigits()
{
int i,j,tmp,a[DIGIT]={1},b[DIGIT]={1};
for(i=3;!a[DIGIT-1];i++){
for(j=0;j<DIGIT;j++){
tmp=a[j];
a[j]+=b[j];
if(j){
a[j]+=a[j-1]/10;
a[j-1]%=10;
}
b[j]=tmp;
}
}
return i-1;
}
int main(void)
{
printf("%d\n",fibDigits(DIGIT));
return 0;
}
Answer
4782
SPEAK / ADD YOUR COMMENT
Comments are moderated.
Posts