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.

Solution

class Solution:
    def tribonacci(self, n: int) -> int:
        if n == 0:
            return 0
        if n == 1 or n == 2:
            return 1

        t0, t1, t2 = 0, 1, 1
        for i in range(3, n + 1):
            t = t0 + t1 + t2
            t2, t1, t0 = t, t2, t1

        return t