C语言——获取本年周数

int week[] = {4,5,6,7,1,2,3};  // 1970年1月1日 一周的星期排序

// 获取本年周数号
static int iYearWeek(int iYear, int iYDay)
{
  int i;
  int iNYear, iNYDay;   // struct tm *t; t->tm_year + 1900;  t->tm_yday + 1;
  int iYearSum = 0;     // 距1970年多少天 
  int iDay, iWeekDay, iWeeks, iRetWeek;

  iNYear = iYear + 1900;
  iNYDay = iYDay + 1;

  for (i = 1970; i < iNYear; i++) {
    if (i % 4 == 0 && i % 100 != 0 || i % 400 == 0) {
      iYearSum += 366;
    }
    else{
      iYearSum += 365;
    }
  }

  // 本年度一月一号距70年的天数取余
  iDay = iYearSum % 7;
  iWeekDay = week[iDay];

  iWeeks = iNYDay / 7;

  if (iNYDay <= 7 - iWeekDay) {
    iRetWeek = iWeeks + 1;
  } else if (iNYDay == 7) {
    iRetWeek = iWeeks;
  } else if ((iNYDay - 7 + iWeekDay) % 7 == 0) {
    iRetWeek = (iNYDay - 7 + iWeekDay) / 7 + 1;
  } else if (iWeekDay == 7 && (iNYDay - 7 + iWeekDay) % 7 != 0) {
    iRetWeek = (iNYDay - 7 + iWeekDay) / 7 + 1;
  } else {
    iRetWeek = (iNYDay - 7 + iWeekDay) / 7 + 2;
  }

  return iRetWeek;
}