C版传统养牛

CU很多C的大牛们都是养牛出身的，俺现在也开始学习养牛。

来源：

题目：若一头小母牛，从出生起第四个年头开始每年生一头母牛，按此规律，第n年有多少头母牛？

 

C 版本：

 

#include
#include
int Cow_Sum(int Year)
{
        if(Year < 3)
        {
                printf("Cow is 1\n");
                exit(0);
        }
        int i=2;
        double Cow0=0,Cow1=1,Cow2=0,Cow3=0;
        for(i;i<=Year;i++)
        {
                   Cow0=Cow3;
                   Cow3=Cow2+Cow3;
                   Cow2=Cow1;
                   Cow1=Cow0;
        }
        printf("Cow is %0.f\n",Cow1+Cow2+Cow3);
        return(0);
}

main(int argc,char *argv[])
{
        if(argc < 2)
        printf("Please input %s year:\n",argv[0]);
        else
        {
                Cow_Sum(atoi(argv[1]));
        }
}


shell 版本：

 

#!/bin/bash
[ -z $1 ] && { echo "$0 Year." ;exit 1; }
(( $1 < 3 )) && { echo Cow is 1;exit 0; }
typeset i=1;Year=${1//[!0-9]/ }

Cow=(0 1 0 0)
for((i=2;i<=Year;i++));do
   Cow[0]=${Cow[3]};Cow[3]=$[Cow[2]+Cow[3]]
   Cow[2]=${Cow[1]};Cow[1]=${Cow[0]}
done
echo "Cow is $((Cow[1]+Cow[2]+Cow[3]+Cow[4]))"