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
.
SOLUTION:
class Solution:
def tribonacci(self, n: int) -> int:
if n <= 2:
return [0, 1, 1][n]
a, b, c = 0, 1, 1
for _ in range(n - 2):
a, b, c = b, c, a + b + c
return c
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