编写一个C语言程序,输入一个日期,输出该日期下个月的最后一天!答:include "stdio.h"int leap(int year){int flag;if(year%4==0 && year%100!=0)flag=1;else if (year%400==0)flag=1;else flag=0;return flag;} void main(){ int year,month,day,h;printf("请输入年月日,用逗号隔开:\n");scanf("%d,%d,%d",&year,&month,&day);if(leap(...