509. 斐波那契数-https://leetcode-cn.com/submissions/detail/18913765/

[zhaojianing]

/**
 * @param {number} N
 * @return {number}
 */

var fib = function(N) {
    function fib_(n,a,b){
        if(n==0)  return a
        else return fib_(n-1,b,a+b)
   }
   return fib_(N,0,1)
};

[zhaojianing]

执行用时：76 ms