1137. N-th Tribonacci Number
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 <= 2³¹ — 1.
class Solution {
/**
time : O(n)
space : O(n)
*/
Map<Integer,Integer> cache=new HashMap<>();
public int tribonacci(int n) {
if(n==0) return 0;
else if(n==1 || n==2) return 1;
else if(cache.containsKey(n)) return cache.get(n);
cache.put(n,tribonacci(n-1)+tribonacci(n-2)+tribonacci(n-3));
return cache.get(n);
}
}
/**
1137. N-th Tribonacci Number
Solved
Easy
Topics
Companies
Hint
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.
*/
