第九章 9．1 定义一个结构体变量（包括年、月、日）。计算该日在本年中是第几天，注意闰年问题。 解：Struct {int year; int month; int day; } date; main() {int days; printf(“Input year,month,day:”); scanf(“%d,%D,%d”,&date.year,&date.month,&date.day); switch(date.month) {case 1: days=date.day; break; case 2: days=date.day+31; break; case 3: days=date.day+59; break; case 4: days=date.day+90; break; case 5: days=date.day+120; break; case 6: days=date.day+31; break; case 7: days=date.day+181; break; case 8: days=date.day+212; break; case 9: days=date.day+243; break; case 10: days=date.day+273; break; case 11: days=date.day+304; break; case 12: days=date.day+334; break; } if((date.year%4==0&&date.year%100!=0||date.year%400==0)&&date.month>=3)days+=1; printf(“\n%d/%d is the %dth day in%d.”,date.month,data.day,days,date,year); } 9.2 写一个函数 days,实现上面的计算。由主函数将年、月、日传递给 days 函数，计算后将日数传回主函数输出。 解：struct y_m_d {int year: int month; int day; } date; intdays(struct y_m_d date1) {int sum; switch(data.month) {case 1:sum=date1.day; break; case 2:sum=date1.day+31; break; case 3:sum=date1.day+59; break; case 4:sum=date1.day+90; break; case 5:sum=date1.day+120; break; case 6:sum=date1.day+151; break; case 7:sum=date1.day+181; break; case 8:sum=date1.day+212; break; case 9:sum=date1.day+243; break case 10:sum=date1.day+243; break case 11:sum=date1.day+243; break case 12:sum=date1.day+243; break } }; 9.3 编写一个函数print,打印一个学生的成绩数，该数组中有5 个学生的数据记录，每个记录包括num、name、sore[3]，用主函数输入这些记录，用 print 函数输出这些记录。 解： #define N 5 struct student {char num[6]; char name[8]; int score[4]; }stu[N]; main() {int I,j ; for(I=0;I
