N-th Tribonacci Number

Read Time:36 Second

The Tribonacci sequence T_n 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

class Solution {
    public int tribonacci(int n) {
            if(n==0){
                return 0;
            }
            if(n==1){
                return 1;
            }
             if(n==2){
                return 1;
            }
            int sum=2;
            int a=0;int b=1;int c=1;

         while(n>2){
                sum=a+b+c;

                a=b;
                b=c;
                c=sum;      
                    n--;
         } 
          return sum;

    }
}