技術標籤：java演算法

問題描述
斐波那契數列指的是這樣一個數列：
1,1,2,3,5,8,13,21…
這個數列從第3項開始，每一項都等於前兩項之和。
設an為該數列的第n項(),那麼這句話可以寫成如下形式：

遞迴實現

import java.util.Scanner;   
public class java1206 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num = scanner.nextInt();
        System.out.println(fib(num));
    }

    public static int fib(int n) {
        if (n == 1 || n == 2) {
            return 1;
        }
        return fib(n - 1) + fib(n - 2);
    }
}
 

非遞迴

import java.util.Scanner;   
public class java1206 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num = scanner.nextInt();
        System.out.println(fib(num));
    }

    public static int fib(int n) {
        int last1 = 1;
        int last2 = 1;
        int cur = 0;
        for (int i = 3; i <= n; i++) {
            cur = last1 + last2;
            last2 = last1;
            last1 = cur;
        }
        return cur;
    }
}