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Tested Python solution for LeetCode 1137 with 17 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 1137 # by problem number
lcpy gen -s n_th_tribonacci_number # by problem name
n, return the value of Tn.
Input: n = 4
Output: 4
Explanation:
T_3 = 0 + 1 + 1 = 2
T_4 = 1 + 1 + 2 = 4
Input: n = 25
Output: 1389537
0 <= n <= 37answer <= 2^31 - 1.class Solution:
# Time: O(n)
# Space: O(1)
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 _ in range(3, n + 1):
t0, t1, t2 = t1, t2, t0 + t1 + t2
return t2
| Time | Space |
|---|---|
| O(n) | O(1) |