1. Fibonacci Number
Oct 20, 2020
The Fibonacci numbers, commonly denoted F(n)
form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0
and 1
. That is,
F(0) = 0, F(1) = 1
F(N) = F(N - 1) + F(N - 2), for N > 1.
Given N
, calculate F(N)
.
Example 1:
Input: 2
Output: 1
Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.
Example 2:
Input: 3
Output: 2
Explanation: F(3) = F(2) + F(1) = 1 + 1 = 2.
Example 3:
Input: 4
Output: 3
Explanation: F(4) = F(3) + F(2) = 2 + 1 = 3.
Note:
0 ≤ N
≤ 30.
Solution
class Solution {
public int fibo(int n, Map<Integer,Integer> m) {
if(n ==0 || n==1)
return n;
if(!m.containsKey(n)){
int sol = fibo(n-1,m) + fibo(n-2,m);
m.put(n,sol);
}
return m.get(n);
}
public int fib(int N) {
Map<Integer,Integer> m = new HashMap<>();
int sol = fibo(N,m);
return sol;
}
}