5.5

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

这个代码运行结果为
知识点
1.&&于||
2.if-else
心得体会
1.学会使用&&和||
2.学会区分==和=