Fibonacci Number (LeetCode)

 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.

SOLUTIONS (Java):

class Solution {
    public int fib(int n) {
        int x=0, y=1, sum=0;
        if(n==0 || n==1)
                return n;
        else{
        for(int i=2; i<=n;i++){
              sum= x+y;
              x=y;
              y=sum;
            }
        }
        return sum;
    }
}