[LintCode] 366 Fibonacci

Description
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 ...


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


Example
Given 1, return 0
Given 2, return 1
Given 10, return 34

Code

class Solution {
    /**
     * @param n: an integer
     * @return an integer f(n)
     */
    public int fibonacci(int n) {
        // write your code here
        if (n == 1) {
            return 0;
        }
        if (n == 2) {
            return 1;
        }
        int prevPrev = 0;
        int prev = 1;
        int result = 0;
        for (int i = 3; i <= n; i++) {
            result = prev + prevPrev;
            prevPrev = prev;
            prev = result;
        }
        return result;
    }
}