N-th Tribonacci Number — LeetCode 1137 Python Solution

The problem

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

Input

n = 4

Output

4

Explanation

T_3 = 0 + 1 + 1 = 2

Python solution

class Solution:
    def tribonacci(self, n: int) -> int:
        a, b, c = 0, 1, 1
        for _ in range(n):
            a, b, c = b, c, a + b + c
        return a

Complexity

Pattern: Dynamic Programming

Define a state, write the transition, and stop recomputing the same subproblem. LeetCode 1137. N-th Tribonacci Number is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Dynamic Programming and Memoization.

The dynamic programming guide has the Python template for the pattern and the 481 LeetCode problems that use it.

Related problems