1. 计算日期到天数转换

输出示例:

思路：计算前n-1个月的天数在加上这个月的天数。

#include <iostream>
using namespace std;int main() {int year, month, day;cin >> year >> month >> day;int month_day[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };int i = 0;int days = 0;for (i = 0; i < month; i++){days += month_day[i];}days += day;if(month > 2 && (((year % 4 == 0) && (year % 100 != 0)) || (year % 400) == 0)){days += 1;}cout << days;return 0;
}

2. 日期累加

输出示例:

思路：直接加到天上，在进位求出日期

#include <iostream>
using namespace std;int GetMonthDay(int year ,int month)
{int months[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };int day = months[month];if (month == 2 &&( ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0))){day++;}return day;
}int main() {int n = 0;cin >> n;int year = 0,month = 0, day = 0,num;while (n-- && (cin >> year >> month >> day >> num) ) { day += num;while (day > GetMonthDay(year,month)){day -= GetMonthDay(year,month);month++;if (month == 13){month = 1;year++;}}printf("%04d-%02d-%02d\n", year, month, day);}
}

3. 打印日期

输出示例:

思路：从这年的1月1开始加，但是注意要要减掉一天，比如：求这一年的第一天的日期，就是1月1号，也可以理解为从1月0号开始加，所以直接加到天上，在进位求日期

#include <iostream>
using namespace std;int GetMonthDay(int year,int month)
{int months[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };int day = months[month];if (month == 2 && ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0) )){day += 1;}return day;
}int main() {int year = 0;int n = 0;while (cin >> year >> n) { //从这年的1月1开始加,但是要减一天int month = 1;int day = n;//1 + n - 1while (day > GetMonthDay(year,month) ){day -= GetMonthDay(year,month);month++;if (month == 13){year++;month = 1;}}printf("%4d-%02d-%02d\n",year,month,day);}
}

4. 日期差值

输出示例:

思路：直接从这天开始加，加到相等为止，每加一天就记一次数。

#include <iostream>
using namespace std;int GetMonthDay(int year,int month)
{int months[] = {0,31,28,31,30,31,30,31,31,30,31,30,31};int day = months[month];if (month == 2 && (((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0))){day++;}return day;
}void Add(int& year,int& month,int& day)
{day += 1;while (day > GetMonthDay(year,month)){day -= GetMonthDay(year,month);month++;if (month == 13){month = 1;year++;}}
} int main() {int year1,month1,day1;scanf("%4d%2d%2d",&year1,&month1,&day1);int year2,month2,day2;scanf("%4d%2d%2d",&year2,&month2,&day2);int count = 0;int flag = 0;if (year2 > year1){flag = 1;}else if (year1 == year2 && month1 < month2){flag = 1;}else if (year1 == year2 && month1 == month2 && day1 < day2){flag = 1;}if (flag == 1){swap(year1,year2);swap(month1,month2);swap(day1,day2);}while (!(year1 == year2 && month1 == month2 && day1 == day2)){Add(year2,month2,day2);count++;}cout << count + 1;
}