Stack Overflow error occurs when using recursive fibonacci function

Question

Here\'s my code and it runs well with values of 400 to 4000 but once it\'s about 4mil, I get stack overflow errors.

Thanks in advance!

public class F         


        

Answer 1

As Jon Skeet above mentioned, your code would require a huge amount of time to run - 2 to the 4 million, which is not practical in any way. Frankly i'm surprised the stack ran dry at all, I'd think the code would just run for a ridiculous amount of time.

You should use an iterative approach. Here's a nicer implementation of the fibonacci sequence:

static long fib(long i){
    if ( i == 0 || i == 1 ) return 1;
    long a = 1; //This is the 0th element 
    long b = 1; //This is the 1st element
    while( i-- > 1 ){ //Each iteration, sets a and b to the next element in the fibonacci sequence
        long temp = b;
        a += b;
        b = a;
        a = temp;
    }
    return b;
}