Fibonacci

最新推荐文章于 2024-10-22 08:54:27 发布

zjj2015

最新推荐文章于 2024-10-22 08:54:27 发布

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本文介绍了一个用于计算斐波那契数列中第N个数字的算法实现。斐波那契数列从0和1开始，之后每个数字都是前两个数字之和。通过迭代方法高效地实现了该功能，并确保了结果不会超出32位有符号整数的最大值。

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Find the Nth number in Fibonacci sequence.

A Fibonacci sequence is defined as follow:

The first two numbers are 0 and 1.
The i th number is the sum of i-1 th number and i-2 th number.
The first ten numbers in Fibonacci sequence is:

0, 1, 1, 2, 3, 5, 8, 13, 21, 34 …

Have you met this question in a real interview? Yes
Example
Given 1, return 0

Given 2, return 1

Given 10, return 34

Note
The Nth fibonacci number won’t exceed the max value of signed 32-bit integer in the test cases.

class Solution {
    /**
     * @param n: an integer
     * @return an integer f(n)
     */
    public int fibonacci(int n) {
        if (n < 0) return -1;
        if (n == 1) return 0;
        if (n == 2) return 1;

        int fn = 0, fn1 = 1, fn2 = 0;
        for (int i = 3; i <= n; i++) {
            fn = fn1 + fn2;
            fn2 = fn1;
            fn1 = fn;
        }

        return fn;
    }
}