1.#include<stdio.h>int main(){ int year =1000; int k = 0; while ((year >= 1000) && (year < 1999)) { if ((year % 400 == 0) || ((year % 100 != 0) && (year % 4 == 0))) { printf("%d是闰年\t", year);//t是制表符 k++; if (k % 3 == 0) printf("\n"); } year = year++; } return(0);}2.#include<stdio.h>int main(){ int month, days , year, a; scanf_s("%d ", &year); scanf_s("%d ", &month); if ((year % 400 == 0) ||((year % 4 == 0) && (year % 100 != 0))) a = 0; else a = 1; switch (month)//开关分支语句 { case 1:case 3:case 5:case 7:case 8:case 10:case 12:days = 31; break;//用来跳出 case 4:case 6:case 9:case 11:days = 30; break; case 2: if (a == 1) days = 28; else days = 29; break; default://相当于else printf("data error"); break; printf("天数为：%d", days); } return 0;}