N-th Tribonacci Number Calculation

1137. N-th Tribonacci Number
Difficulty: Easy
Topics: Math, Dynamic Programming, Memoization
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, i.e. answer <= 231 - 1.

Hint:

Make an array F of length 38, and set F[0] = 0, F[1] = F[2] = 1.
Now write a loop where you set F[n+3] = F[n]...