Fibonacci

题目：

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 ...

补充： (2016-10-30) 特殊处理一个情况就是第1个和第2个fib的情况。长期不coding忘记了特殊情况的重要性

分析：

看题意，特别注意0，1，2，3时候的输入

解法：

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 == 1) {
            return 1;
        }
        int a = 0;
        int b = 1;
        for (int i = 2; i <= n; i++) {
            int temp = a + b;
            b = a;
            a = temp;
        }
        return a;
    }
}