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1236. N Th Tribonacci Number

Math Dynamic Programming Memoization

Problem - 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.

 

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.

Solutions

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class Solution:
    def tribonacci(self, n: int) -> int:
        i, j, k = 0, 1, 1
        for _ in range(n):
            i, j, k = j, k, i + j + k
        return i

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 17.7 MB (78.58%)