/*
* @lc app=leetcode.cn id=509 lang=javascript
*
* [509] 斐波那契数
*/
// @lc code=start
/**
* @param {number} n
* @return {number}
*/
var fib = function (n) {
if (n === 0) return 0;
if (n === 1) return 1;
return fib(n - 1) + fib(n - 2);
};
/*
* @lc app=leetcode.cn id=509 lang=javascript
*
* [509] 斐波那契数
*/
// @lc code=start
/**
* @param {number} n
* @return {number}
*/
var fib = function (n, arr = []) {
if (arr[n]) return arr[n];
if (n === 0) return 0;
if (n === 1) return 1;
arr[n] = fib(n - 1, arr) + fib(n - 2, arr);
return arr[n];
};
var fib = function (n) {
let a = 0,
b = 1
if (n < 2) return n
for (let i = 0; i <= n - 2; i++) {
const c = a + b
a = b
b = c
}
return b
};