Fibonacci Numbers: a series of numbers where the first two numbers are 0 and 1 respectively, and the following number is the sum of two preceding numbers. (0, 1, 1, 2, 3, 5, 8, 13 ···)

Recursive Approach:

Memoization: We use a table to store key-value pairs where the key is n, and the value is fib(n). If key is in the table, we can return instantly.

斐波那契数列定义：斐波那契数列，又称黄金分割数列。它指的是这样一个数列：0, 1, 1, 2, 3, 5, 8, 13 ···

Recursion Approach:

Memoization: 勾选此处，就会显示出现一个存储列表，它存储key和对应的值。其中k为n，其值为fib(n)。 如果发现key在表中，就可以立即return。