PAT乙级(Basic Level)练习题 >母牛的故事

题目：


思路：f(n)=f(n-1)+f(n-3) n>=4
f(0)=1, f(1)=2, f(2)=3, f(3)=4

代码如下：

import java.util.*;public class PAT1007 {    public static void main(String[] args) {        // TODO Auto-generated method stub        Scanner in = new Scanner(System.in);        long []a = new long[55];        a[0]=1;        a[1]=2;        a[2]=3;        a[3]=4;        for(int i = 4;i<55;i++){            a[i]=a[i-1]+a[i-3];        }        while(in.hasNext()){            int n = in.nextInt();            System.out.println(a[n-1]);        }    }}