原题链接 http://projecteuler.net/problem=25

1000-digit Fibonacci number

The Fibonacci sequence is defined by the recurrence relation:

F(n) = F(n-1)+ F(n-2), where F₁ = 1 and F₂ = 1.

Hence the first 12 terms will be:

F₁ = 1
F₂ = 1
F₃ = 2
F₄ = 3
F₅ = 5
F₆ = 8
F₇ = 13
F₈ = 21
F₉ = 34
F₁₀ = 55
F₁₁ = 89
F₁₂ = 144

The 12th term, F₁₂, is the first term to contain three digits.

What is the first term in the Fibonacci sequence to contain 1000 digits?

1000个数字的斐波纳契数

斐波那契数列由如下递归关系定义：

F(n) = F(n-1)+ F(n-2), 且 F₁ = 1 ，F₂ = 1

因此数列的前12项为：

F₁ = 1
F₂ = 1
F₃ = 2
F₄ = 3
F₅ = 5
F₆ = 8
F₇ = 13
F₈ = 21
F₉ = 34
F₁₀ = 55
F₁₁ = 89
F₁₂ = 144

第12项，即是第一个包含三个数字的项

求数列中第一个包含1000个数字的项

解法：

用第二题中的方法，生成斐波那契数列，之后判断。