[leetCode] 1137. N-th Tribonacci Number (Python)

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:
        fiboNum = 0
        
        if n == 1:
            fiboNum = 1
        elif n == 2:
            fiboNum = 1
        elif n == 3:
            fiboNum = 2
        elif n > 3:
            fibo = [0] * (n)
            fibo[0] = 1
            fibo[1] = 1
            fibo[2] = 2

            for i in range(3, n):
                fibo[i] = fibo[i-1] + fibo[i-2] + fibo[i-3]

            fiboNum = fibo[n-1]
            
        return fiboNum

SOMJANG/CODINGTEST_PRACTICE