要求：输入某年某月某日，判断这一天是这一年的第几天，使用C语言实现

#include<stdio.h>

int dayYear(int year,int month,int day){
    int days_in_month[] = {0,31,28,31,30,31,30,31,31,30,31,30,31};
    int i,days=0;

    for(i=1;i<month;i++){
        days += days_in_month[i];
    }

    if(((year%4==0)&&(year%100!=0))||(year%400==0)){
        if(month>2)
        days++;
    }
    days += day;

    return days;
}

int main(){
    int year,month,day;

    printf("请输入年月日（格式为YYYY/MM/DD）：");
    scanf("%d%d%d",&year,&month,&day);

    int result = dayYear(year,month,day);

    printf("%d年%d月%d日是%d年的第%d天\n",year,month,day,year,result);

    return 0;
}

测试结果：

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