按月、按天计算失效日期的代码实现

按月、按天计算失效日期的代码实现

【背景】：在我们计算截止日期、失效时期的时候，可能存在按年、按月、按天统计失效的情况。比如：当前日期是2014-12-22,900天后失效，失效日期是多少？17个月后失效，失效日期是多少。通过本文源码，你都可以得到答案。

为验证程序的正确性，本文对每个接口函数都做了大量的测试用例。

 

// sn_ctrl.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include <assert.h>
#include <iostream>
using namespace std;

const int MAX_MONTH_CNTS_IN_YEAR = 12;

/*
**@brief:判定年份是否为闰年.
**@param: iYear当前年份.
**@return:true,闰年; false,平年.
*/
bool IsLeapYear(unsigned int iYear)
{
  if ( (iYear%4 == 0 && iYear%100 != 0) || (iYear%400 == 0) )
  {
    return true;
  }
  else
  {
    return false;
  }
}

/*
**@brief:判定某年某月的天数.
**@param: iYear当前年份，iMonth当前月份;
**@return:当前年、月的天数.
*/
unsigned int daysInMonth(unsigned int iYear, unsigned int iMonth)
{
  assert(iMonth >=1 && iMonth <= MAX_MONTH_CNTS_IN_YEAR);
  int iDaysInMonth = 0;
  switch(iMonth)
  {
    case 1:
    case 3:
    case 5:
    case 7:
    case 8:
    case 10:
    case 12:
      iDaysInMonth = 31;
    break;
    case 4:
    case 6:
    case 9:
    case 11:
      iDaysInMonth = 30;
    break;
    case 2:
      if (IsLeapYear(iYear))
      {
        iDaysInMonth = 29;
      }
      else
      {
        iDaysInMonth = 28;
      }
    break;
    default:
      cout << "Error Month!!" << endl;
      break;
  }
  return iDaysInMonth;
}


struct Date
{
  unsigned int date_year;
  unsigned int date_month;
  unsigned int date_day;
};

class DateOp
{
public:
  DateOp(){}
  DateOp(Date thisDate):theDate(thisDate){}
  virtual ~DateOp(){}
  Date DataAddmonths(Date date_init, unsigned int month_cnts);
  Date DateAddDays(Date date_init, unsigned int day_cnts);

private:
  Date theDate;
};

/*
**@brief:初始月份加几个月后的日期.
**@param: dateInit初始日期，iMonthCnts过几个月;
**@return:计算后的新的日期.
*/
Date DateOp::DataAddmonths(Date dateInit, unsigned int iMonthCnts)
{
  assert (iMonthCnts >= 1);
  Date dateAfterAdd = dateInit;

  unsigned int iMonthNewPos = dateInit.date_month + iMonthCnts;
  if (iMonthNewPos > MAX_MONTH_CNTS_IN_YEAR)  //求和后超过12
  {
    unsigned int iYearCnts = (iMonthNewPos)/(MAX_MONTH_CNTS_IN_YEAR);
    unsigned int iMonthNew = (iMonthNewPos)%(MAX_MONTH_CNTS_IN_YEAR);
    if (0 == iMonthNew) //月份为0特殊处理
    {
      dateAfterAdd.date_year = dateInit.date_year + iYearCnts -1;
      iMonthNew = 12;
    }
    else
    {
      dateAfterAdd.date_year = dateInit.date_year + iYearCnts;
    }  
    dateAfterAdd.date_month = iMonthNew;
  
  }
  else  //求和后不超过12
  {
    dateAfterAdd.date_year = dateInit.date_year;
    dateAfterAdd.date_month = dateInit.date_month + iMonthCnts;
  }

  //2月份特殊处理
  if ( (30 == dateInit.date_day || 31 == dateInit.date_day) && (2 == dateAfterAdd.date_month))
  {
    dateAfterAdd.date_day = daysInMonth(dateAfterAdd.date_year, dateAfterAdd.date_month);
  }
  //30天的月份特殊处理
  else if ((31 == dateInit.date_day) && ((4 == dateAfterAdd.date_month) || (6 == dateAfterAdd.date_month) ||
         (9 == dateAfterAdd.date_month) || (11 == dateAfterAdd.date_month)))
  {
    dateAfterAdd.date_day = 30;
  }
  else
  {
    dateAfterAdd.date_day = dateInit.date_day;
  }
  return dateAfterAdd;
}

/*
**@brief:初始月份加*天后的日期.
**@param: dateInit初始日期，iMonthCnts过多少天;
**@return:计算后的新的日期.
*/
Date DateOp::DateAddDays(Date dateInit, unsigned int day_cnts)
{
  assert(day_cnts >= 1);
  cout << "+ " << day_cnts << endl;
  Date dateAfterAdd = dateInit;

  unsigned int iCurDaysInMonth = daysInMonth(dateInit.date_year, dateInit.date_month); //当前月的总天数.
  //cout << "iCurDaysInMonth = " << iCurDaysInMonth << endl;
  int iDayTotal = day_cnts;
  if (dateInit.date_day + day_cnts <= iCurDaysInMonth)
  {
    dateAfterAdd.date_day = dateInit.date_day + day_cnts;
    return dateAfterAdd;
  }

  int iLeftDaysInCurMonth = iCurDaysInMonth - dateInit.date_day; //当前月剩余天数.
  //cout << endl << "iDayTotal = " << iDayTotal << "\t iLeftDayInCurmonth = " << iLeftDaysInCurMonth << endl << endl;
  //cout << "iAvgMonthCnts = " << iAvgMonthCnts << endl << endl;

  unsigned int iDaysInMonth = 0;
  int iLeftDaysTotal = 0;  //统计大约几个月的实际总天数.
  unsigned int iMonthCnts = 0;
  while (iLeftDaysTotal <= iDayTotal - iLeftDaysInCurMonth)
  {
    ++iMonthCnts;
    unsigned int iCurMonth = dateInit.date_month + iMonthCnts;
  // cout << "iCurMonth = " << iCurMonth << endl;
    unsigned int iYearCnts = 0;
    if (iCurMonth > 12)
    {
      iYearCnts = (iCurMonth)/(MAX_MONTH_CNTS_IN_YEAR);
    }
  
    //cout << "iYearCnts = " << iYearCnts << endl;

    if (0 == iYearCnts)
    {
      dateAfterAdd.date_year = dateInit.date_year;
      dateAfterAdd.date_month = iCurMonth;
      iDaysInMonth = daysInMonth(dateInit.date_year, iCurMonth);
      iLeftDaysTotal += iDaysInMonth;
    }
    else
    {
      unsigned int iMonthNew = (iCurMonth)%(MAX_MONTH_CNTS_IN_YEAR);
      if (0 == iMonthNew) //月份为0特殊处理
      {
        dateAfterAdd.date_year = dateInit.date_year + iYearCnts -1;
        iMonthNew = 12;
      }
      else
      {
        dateAfterAdd.date_year = dateInit.date_year + iYearCnts;
      }
      dateAfterAdd.date_month = iMonthNew;
      iDaysInMonth = daysInMonth(dateAfterAdd.date_year, iMonthNew);
      iLeftDaysTotal += iDaysInMonth;
      
    }//end else
    //对于超出的做特殊处理.
    if (iLeftDaysTotal > (iDayTotal - iLeftDaysInCurMonth))
    {
      iLeftDaysTotal -= iDaysInMonth;
      break;
    }
  }

  //cout << "iDayTotal  =" << iDayTotal << "\tiLeftDaysInCurMonth = " << iLeftDaysInCurMonth  //bug??
    //<< "\tiLeftDaysTotal = " << iLeftDaysTotal << endl;
  if (iDayTotal - iLeftDaysInCurMonth - iLeftDaysTotal < 0)
  {
    dateAfterAdd.date_day = iDayTotal - iLeftDaysInCurMonth;
  }
  else
  {
    dateAfterAdd.date_day = iDayTotal - iLeftDaysInCurMonth - iLeftDaysTotal;
  }
  
  if (dateAfterAdd.date_month > 12)
  {
    dateAfterAdd.date_year += 1;
    dateAfterAdd.date_month = 1;
  }
  if (dateAfterAdd.date_day == 0)
  {
    if (1 == dateAfterAdd.date_month)
    {
      dateAfterAdd.date_month = 12;
      dateAfterAdd.date_year -= 1;
    }
    else
    {
      dateAfterAdd.date_month -= 1;
    }

    dateAfterAdd.date_day = daysInMonth(dateAfterAdd.date_year, dateAfterAdd.date_month);
  }
  assert((dateAfterAdd.date_month >= 1) && (dateAfterAdd.date_month <= 12));
  assert((dateAfterAdd.date_day >= 1) && (dateAfterAdd.date_day <= 31));
  return dateAfterAdd;
}

/*
**@brief:打印日期格式.
**@param: theDate提供打印的日期
**@return:空.
*/
void DisplayDate(Date& theDate)
{
  cout << theDate.date_year << "/" << theDate.date_month 
     << "/" << theDate.date_day << "\t";
  cout << endl << endl;
}


/*
**@brief:测试用例:测试某年是否为闰年.
**@param: 空.
**@return:空.
*/
void testLeapYearOrNot()
{
  unsigned int iBeginYear=1900;
  unsigned int iEndYear=3000;

  cout << "From " << iBeginYear << " To " << iEndYear << endl;

  for (unsigned int iYear = iBeginYear; iYear <= iEndYear; ++iYear)
  {
    if (IsLeapYear(iYear))
    {
      cout << iYear << "\t";
    }
  }
  cout << endl;
}


/*
**@brief:单元测试用例，某年某月有多少天.
**@param: 空.
**@return:空.
*/
void testDaysInMonth()
{
  unsigned int iBeginYear = 1980;
  unsigned int iEndYear = 2020;
  unsigned int iBeginMonth = 1;
  unsigned int iEndMonth = 12;
  unsigned int iDaysOfYear = 0;

  for (unsigned int iYear = iBeginYear; iYear <= iEndYear; ++iYear)
  {
      iDaysOfYear = 0;
    cout << "Year:" << iYear << endl;
    for (unsigned int iMonth = iBeginMonth; iMonth <= iEndMonth; ++iMonth)
    {

      unsigned int iDaysInmonth = daysInMonth(iYear,iMonth);
      iDaysOfYear += iDaysInmonth;
      cout << iDaysInmonth << "\t";
    }

    cout << endl;
    cout << iYear << " has " << iDaysOfYear << " days!" << endl << endl;
  }
}

/*
**@brief:单元测试用例，测试几个月后日期.
**@param: 空.
**@return:空.
*/
void testDataAddmonths()
{
  unsigned int iBeginYear = 2014;
  unsigned int iEndYear = 2015;

  unsigned int iBeginMonths = 1;
  unsigned int iEndMonths = 30;

  Date beginDate;
  beginDate.date_year = 1980;
  beginDate.date_month = 1;
  beginDate.date_day = 31;
  Date endDate = beginDate;
  DateOp dateOp;

  for (unsigned int iYear = iBeginYear; iYear <= iEndYear; ++iYear)
  {
    beginDate.date_year = iYear;
    (void)DisplayDate(beginDate);
    cout << endl;
    for (unsigned int iMonth = 1; iMonth <= MAX_MONTH_CNTS_IN_YEAR; ++iMonth)
    {
      beginDate.date_month = iMonth;
      cout << iMonth << "\t";
      for (unsigned int iMonthCnts = iBeginMonths; iMonthCnts <= iEndMonths; ++iMonthCnts)
      {
        endDate = dateOp.DataAddmonths(beginDate, iMonthCnts);
        cout << " +" << iMonthCnts << " ";
        (void)DisplayDate(endDate);
      }//end for iMonthCnts;
      cout << endl << endl;
    }//end for iMonth
    cout << endl << endl << endl;
  }//end for iYear
}

/*
**@brief:单元测试用例，测试给定天后的日期.
**@param: 空.
**@return:空.
*/
void testDataAddDays()
{
  Date beginDate;
  beginDate.date_year = 1988;
  beginDate.date_month = 7;
  beginDate.date_day = 19;
  
  DateOp dateOp;
  cout << "Init Date is :" << endl;
  (void)DisplayDate(beginDate);

  Date endDate = beginDate;



  endDate = dateOp.DateAddDays(beginDate, 1); //1988-7-20
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 12); //1988-7-31
  (void)DisplayDate(endDate); 


  endDate = dateOp.DateAddDays(beginDate, 13); //1988-8-1
  (void)DisplayDate(endDate); 


  endDate = dateOp.DateAddDays(beginDate, 100); //1988-10-27
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 200); //1989-2-4
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 500); //1989-12-1
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 954); //1991-2-28
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 955); //1991-3-1
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 1000); //1991年4月15日星期一
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 2000); //1994年1月9日星期日
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 5000); //2002年3月28日星期四
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 10000); //2015年12月5日星期六 
  (void)DisplayDate(endDate);

  endDate = dateOp.DateAddDays(beginDate, 20000); //2043年4月22日星期三 
  (void)DisplayDate(endDate);

}

int _tmain(int argc, _TCHAR* argv[])
{
  Date thisDate;
  thisDate.date_year = 2014;
  thisDate.date_month = 2;
  thisDate.date_day = 21;

  Date endDate = thisDate;

  DateOp thisDateOp(thisDate);
  (void)DisplayDate(thisDate);

  //不同类型用例测试.
  (void)testLeapYearOrNot();
  (void)testDaysInMonth();
  (void)testDataAddmonths();
  (void)testDataAddDays();
  return 0;
}

             【按天计算失效日期流程描述】

              第一步：确认当前月份到月末还剩余几天（记作A），如果传入的失效天数<剩余天数，则返回原有年份、原有月份、新增天数即可；

                            如果传入的失效天数>剩余天数，则记录下失效天数-剩余天数A的差值（记作B），进入第二步；

              第二步：循环判定下个月、下下个月....下Next N个月的总天数之和是否>第一步的差值，如果小于，则继续循环判定；

                            如果大于，则统计记录下当前月份、年份，并将月份减去1，并统计出循环的总天数C，进入第三步；

              第三步：计算失效月的具体哪一天，根据B-C的值就是失效对应的那一天。

                       

              【 注意事项】：

              需要对月份、天数进行特殊判定，如1<=月份<=12；1<=天<=31；特定月份2月的平年、闰年处理；以及4,6,9.11 30天的处理。
        

         代码通过VS2010编译通过，测试案例都没有bug。有发现bug可以留言，一起改进完善，谢谢！

     

作者：铭毅天下