In this post, we are going to solve the problem, 1137. N-th Tribonacci Number problem of Leetcode. This problem 1137. N-th Tribonacci Number is a Leetcode easy level problem. Let’s see the code, 1137. N-th Tribonacci Number – Leetcode Solution.

Problem

The Tribonacci sequence Tn is defined as follows:

T₀ = 0, T₁ = 1, T₂ = 1, and T_n+3 = T_n + T_n+1 + T_n+2 for n >= 0.

Given n, return the value of T_n.

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.

Now, let’s see the code of 1137. N-th Tribonacci Number – Leetcode Solution.

N-th Tribonacci Number – Leetcode Solution

1137. N-th Tribonacci Number – Solution in Java

class Solution {
    public int tribonacci(int n) {
        int a = 0, b = 1, c = 1, ans = 0;
        if(n==0) return 0;
        else if(n==1) return 1;
        else if(n==2) return 1;
        for(int N=3;N<=n;N++){
            ans = a + b + c;
            a = b;
            b = c;
            c = ans;
        }
        return ans;
    }
}

1137. N-th Tribonacci Number – Solution in C++

    int tribonacci(int n) {
        if (n < 2) return n;
        int a = 0, b = 1, c = 1, d = a + b + c;
        while (n-- > 2) {
            d = a + b + c, a = b, b = c, c = d;
        }
        return c;
    }

1137. N-th Tribonacci Number – Solution in Python

    def tribonacci(self, n):
        a, b, c = 1, 0, 0
        for _ in xrange(n): a, b, c = b, c, a + b + c
        return c

Note: This problem 1137. N-th Tribonacci Number is generated by Leetcode but the solution is provided by CodingBroz. This tutorial is only for Educational and Learning purpose.