1 // Copyright 2015 The Bazel Authors. All rights reserved.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 /// Returns the nth Fibonacci number.
16 ///
17 /// # Examples
18 ///
19 /// ```
20 /// assert_eq!(fibonacci::fibonacci(5), 5)
21 /// ```
fibonacci(n: u64) -> u6422 pub fn fibonacci(n: u64) -> u64 {
23 if n < 2 {
24 return n;
25 }
26 let mut n1: u64 = 0;
27 let mut n2: u64 = 1;
28 for _ in 1..n {
29 let sum = n1 + n2;
30 n1 = n2;
31 n2 = sum;
32 }
33 n2
34 }
35
36 #[cfg(test)]
37 mod test {
38 use super::fibonacci;
39
40 #[test]
test_fibonacci()41 fn test_fibonacci() {
42 let numbers: Vec<u64> = vec![0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144];
43 for (i, number) in numbers.iter().enumerate() {
44 assert_eq!(*number, fibonacci(i as u64));
45 }
46 }
47 }
48