5.5

#include <stdio.h>main(){    int year,flag;    printf("Enter year:");    scanf("%d",&year);    if(year/4==0&&year/100!=0)    {        flag=1;    }    else    {        flag=0;    }    if(year/400==0)    {        printf("%d is a leap year!\n",year);    }    else    {        printf("%d is not a leap year!\n",year);    }}

知识点：闰年与平年的编程
心得体会：if语句的应用