Leetcode专题[数组]-剑指offer10-I.-斐波那契数列

leetcode链接：
https://leetcode.cn/problems/fei-bo-na-qi-shu-lie-lcof/soluti...
解题思路：
递归

func fib(n int) int {
    if n == 0 || n == 1 {
        return n
    }
    a,b := 0, 1
    for i := 2; i <= n; i++ {
        a, b = b, (a+b) % 1000000007
    }
    return b
}