1137. N-th Tribonacci Number

Easy
​
The Tribonacci sequence Tn is defined as follows:
T0 = 0, T1 = 1, T2 = 1, and Tn+3 = Tn + Tn+1 + Tn+2 for n >= 0.
Given n, return the value of Tn.
Example 1:
Input: n = 4
Output:
4
Explanation:
T_3 = 0 + 1 + 1 = 2
T_4 = 1 + 1 + 2 = 4
Example 2:
Input: n = 25
Output:
1389537
Constraints:
  • 0 <= n <= 37
  • The answer is guaranteed to fit within a 32-bit integer, ie. answer <= 2^31 - 1.

解題

func tribonacci(n int) int {
arr := []int{0, 1, 1}
​
for i:=3; i<=n; i++ {
arr = append(arr, arr[i-1] + arr[i-2] + arr[i-3])
}
​
return arr[n]
}