My solution to Code challenge #77

Implemented in golang, quite easy to be fair 😄

func GetNthFib(n int) int {
    if n == 1 {
        return 0
    }
    if n == 2 {
        return 1
    }
    x, y := 0, 1
    for i := 2; i < n; i++ {
        x, y = y, x+y
    }
    return y
}

Explanation

So we check for the first two value as this two are required to be able to build the rest of the sequence.

Once we know it is not 0 (x) or 1 (y), we know that the correct result comes from adding the x+y and moving the values 1 place forward.

The loop starts at 2 because otherwise the results will be offset by 2 iterations (we already check the first two statically).

For example, if the loop starts at 0 and they ask for nth 3, then our result will be 3 which is incorrect as the third position on Fibonacci's sequence is 1.

You can play around with it by using this Golang Playground link

Comments

[Evgenij Renke]

Your solution is not correct.
Fibonacci is defined:
Fib(0) = 0
(zero and negative n are more or less optional, depending on your requirements/definition)

Fib(1) = 1
Fib(2) = 1
Fib(n) = (n-1)+(n-2)

Your solution:
Fib(0) = 1
Fib(1) = 0
Fib(2) = 1
Fib(3) = 1
Fib(4) = 2
...

Here is a quick fix:

package main

import (
    "fmt"
)

func main() {
    fmt.Println(getNthFib(4))
}

func getNthFib(n int) int {
    if n == 0 {
        return 0 
    }
    if n == 1 {
        return 1 // x=1
    }

    // this if is theoretical not necessary in this code 
    // because y := 1 -> skip for loop -> directly return y
    // but better for Readability and clean code 
    if n == 2 {
        return 1 // y=1
    }

    x, y := 1, 1
    for i := 2; i < n; i++ {
        x, y = y, x+y
    }
    return y
}