Problem
This problem comes from Project Euler 2
Problem
Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
Solution
If you understand how a Fibonacci sequence works, then the code below is understandable. The solution has been written in both Python and Rust, and either one will work.
# Project Euler: Problem 2
# Even Fibonacci Numbers
fp = 0 # previous fibonacci number
fc = 1 # current fibonacci number
sum = 0
while fc < 4000000:
fn = fc + fp # fn is the next fibonacci number
if (fn % 2 == 0): # if next is divisible by 2
sum += fn
fp = fc # current becomes previous
fc = fn # next becomes current
print(sum)// Project Euler: Problem 2
// Even Fibonacci Numbers
// Alternate Rust version
fn main() {
let mut f_p = 0; // Previous Fibonacci number
let mut f_c = 1; // Current Fibonacci number
let mut sum = 0;
while f_c < 4000000 {
let f_n = f_c + f_p; // f_n is the next Fibonacci number
if f_n % 2 == 0 {
sum += f_n;
}
f_p = f_c;
f_c = f_n;
}
println!("{}", sum);
}