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: 2
Output: 1
Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.
Example 2:
Input: 3
Output: 2
Explanation: F(3) = F(2) + F(1) = 1 + 1 = 2.
Example 3:
Input: 4
Output: 3
Explanation: F(4) = F(3) + F(2) = 2 + 1 = 3.
Note:
0 ≤ N ≤ 30.
/**
* @param {number} N
* @return {number}
*/
var fib = function(N) {
if (N == 0) return 0
if (N == 1 || N == 2) return 1
return fib(N - 1) + fib(N - 2)
}
- Time complexity: O(2^n)- since T(n) = T(n-1) + T(n-2)is an exponential time
- Space complexity: O(n) - space for recursive function call stack