数兔子问题

编程实现：有一对兔子，从出生后第3个月起每个月都生一对兔子，小兔子长到第3个月后每个月又生一对兔子，假如兔子都不死，问每个月的兔子总数为多少？

C代码     

long int get_rabbits_cnt(long int month)
{
	long int cnt = 1;
	long int cnt_pre = 0;
	long int cnt_prepre = 0;
	long int i;
	for(i = 1; i < month; i++)
	{
		cnt_prepre = cnt_pre;
		cnt_pre = cnt;
		cnt = cnt_pre+cnt_prepre;
	}
	return cnt;
}

java代码

public class HelloWorld {
	private static Scanner scan;
	public static void main(String []args){
		scan = new Scanner(System.in);
		long rabbits = 0;
		long month = 0;
		while(true)
		{
	        System.out.println("输入想查询的月数");
	        // 判断是否还有输入
	        if(scan.hasNextLine()){   
	          String str2 = scan.nextLine();
	          System.out.println("输入的数据为："+str2);  
	          month = Integer.parseInt(str2);
	          rabbits = calculate_rabbit(month);
	        } 		
			System.out.println("month:  "+month+"  rabbits pair:  "+rabbits+"  number:  "+(rabbits<<1));			
			
		}
	}
	private static long calculate_rabbit(long month) {
		// TODO Auto-generated method stub
		long cnt = 1;
		long cnt_pre = 0;
		long cnt_prepre = 0;
			long i;
			for(i = 1; i < month; i++)
			{
				cnt_prepre = cnt_pre;
				cnt_pre = cnt;
				cnt = cnt_pre+cnt_prepre;
			}
			return cnt;
	}
}

来自为知笔记(Wiz)