Fibonacci Number - Read / Write

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: n = 2 Output: 1 Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.

Example 2:
Input: n = 3 Output: 2 Explanation: F(3) = F(2) + F(1) = 1 + 1 = 2.

Example 3:
Input: n = 4 Output: 3 Explanation: F(4) = F(3) + F(2) = 2 + 1 = 3.

Solution

class Solution {
    private int[] val = new int[31];
    private int getVal(int n) {
        if(val[n] == 0) {
            val[n] = fib(n);
        }
        return val[n];
    }
    public int fib(int n) {
        if(n <= 0) return 0;
        if(n == 1) return 1;
        return getVal(n-1) + getVal(n-2);
    }
}