509. Fibonacci Number

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.

# @lc code=start
using LeetCode

function fib(n::Int)::Int
    n <= 1 && return n
    pre, cur = 0, 1
    for _ in 2:n
        pre, cur = cur, pre + cur
    end
    return cur
end

# @lc code=end

fib (generic function with 1 method)

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