509. Fibonacci Number

Easy

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

解題

func fib(n int) int {
    arr := make([]int, n+2)
    
    arr[0], arr[1] = 0, 1
    
    for i:=2; i<=n; i++ {
        arr[i] = arr[i-1]+arr[i-2]
    }
    
    return arr[n]
}