Fibonacci Number_503.js

/*509. Fibonacci Number
Easy
Topics
Companies
The Fibonacci numbers, commonly denoted F(n) form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0 and 1. That is,

F(0) = 0, F(1) = 1
F(n) = F(n - 1) + F(n - 2), for n > 1.
Given n, calculate F(n).

 

Example 1:

Input: n = 2
Output: 1
Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.
Example 2:

Input: n = 3
Output: 2
Explanation: F(3) = F(2) + F(1) = 1 + 1 = 2.
Example 3:

Input: n = 4
Output: 3
Explanation: F(4) = F(3) + F(2) = 2 + 1 = 3.
 

Constraints:

0 <= n <= 30
*/



//fib -> num > that many nums in the fib sequnce 
//return last num in seq

function fib(numsGenerated){
   let sequence = [0,1]
    for(let i = 2; i <= numsGenerated; i++){
    let a = sequence[i - 1]
    let b = sequence[i - 2]
     sequence.push(a + b)
   }
       return sequence[numsGenerated]
 }

    console.log( fib(3), '2')
    console.log( fib(5), '5')
    console.log( fib(7), '13')
    

//0,1,1,2,3,5,8,13
//F(3) -> 2
//F(4) -> 3