Fibonacci

Find the Nth number in Fibonacci sequence.

A Fibonacci sequence is defined as follow:

• The first two numbers are 0 and 1.
• The i th number is the sum of i-1 th number and i-2 th number.

The first ten numbers in Fibonacci sequence is:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34 ...

Have you met this question in a real interview? 

Yes

Example

Given 1, return 0

Given 2, return 1

Given 10, return 34

Note

The Nth fibonacci number won't exceed the max value of signed 32-bit integer in the test cases.

class Solution {

    /**

     * @param n: an integer

     * @return an integer f(n)

     */

    public int fibonacci(int n) {

        // write your code here

        if(n <= 2) return n - 1;

        int pre = 0, cur = 1;

        for(int i = 3; i <= n; i++){

            int temp = cur;

            if(Integer.MAX_VALUE - pre < cur) return Integer.MAX_VALUE;

            cur = pre +cur;

            pre = temp;

        }

        return cur;

    }

}