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.
class Solution:
def tribonacci(self, n: int) -> int:
if n == 0:
return 0
elif n == 1:
return 1
elif n == 2:
return 1
t = [0] * (n+2)
t[0] = 0
t[1] = 1
t[2] = 1
for i in range(3, n+1):
t[i] = t[i-1] + t[i-2] + t[i-3]
return t[n]