509. Fibonacci Number

Easy
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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]
}