检查两次是否重叠 - Check if two times overlap

我想看看我从数据库读取的时间是否与用户提供的时间重叠。

我的数据库如下所示：

-----------------------------------------------
|organiser|meeting_start|meeting_end|boardroom|
-----------------------------------------------
| John Doe| 1340193600  | 1340195400| big     |
-----------------------------------------------

我的代码如下所示：

date_default_timezone_set('Africa/Johannesburg');
$from = strtotime($_GET['meeting_date'] . ' ' . $_GET['meeting_start']);
$to = strtotime($_GET['meeting_date'] . ' ' . $_GET['meeting_end']);
$another_meeting = false;
$meeting_date = strtotime($_GET['meeting_date']);
$meeting_next = $meeting_date + 86400;
$result = mysql_query("SELECT meeting_start, meeting_end FROM admin_boardroom_booking WHERE boardroom = '" . $_GET['boardroom'] . "' AND meeting_start >= '" . $meeting_date . "' AND meeting_end < '" . $meeting_next . "'")or die(mysql_error());
while($row = mysql_fetch_array($result)) {
    $from_compare = $row['meeting_start'];
    $to_compare = $row['meeting_end'];
    $intersect = min($to, $to_compare) - max($from, $from_compare);
    if ( $intersect < 0 )
        $intersect = 0;
    $overlap = $intersect / 3600;
    if ( $overlap <= 0 ) {
        $another_meeting = true;
        break;
    }
}
if ($another_meeting)
    echo 'ERROR';

如果我故意输入两个重叠时间，它不会回显错误。我做错了什么？

两个时间段 P1 和 P2 重叠，当且仅当以下条件中至少有一个成立：

P1 在 P2 的开始和结束之间开始（ P2.from <= P1.from <= P2.to ）
P2 在 P1 的开始和结束之间开始（ P1.from <= P2.from <= P1.to ）

这将捕获部分重叠的时期以及一个完全覆盖另一个的时期。如果其中一个周期重叠，则必须始终在另一个周期内开始（或结束）。

因此，$another_meeting将定义如下：

$another_meeting = ($from >= $from_compare && $from <= $to_compare) ||
                   ($from_compare >= $from && $from_compare <= $to);

您可能希望将边界情况更改为严格<检查一个事件是否可以与另一个事件同时结束。

只是在做类似的事情....但只是随着时间的流逝....

$startTime = strtotime("7:00");
$endTime   = strtotime("10:30");
$chkStartTime = strtotime("10:00");
$chkEndTime   = strtotime("12:10");
if($chkStartTime > $startTime && $chkEndTime < $endTime)
{
    // Check time is in between start and end time
    echo "1 Time is in between start and end time";
}
elseif(($chkStartTime > $startTime && $chkStartTime < $endTime) || ($chkEndTime > $startTime && $chkEndTime < $endTime))
{
    // Check start or end time is in between start and end time
    echo "2 ChK start or end Time is in between start and end time";
}
elseif($chkStartTime==$startTime || $chkEndTime==$endTime)
{
    // Check start or end time is at the border of start and end time
    echo "3 ChK start or end Time is at the border of start and end time";
}
elseif($startTime > $chkStartTime && $endTime < $chkEndTime)
{
    // start and end time is in between  the check start and end time.
    echo "4 start and end Time is overlapping  chk start and end time";
}

我可能会用这样的东西来解决它：

function avaliable($start, $end) {
  // checks if there's a meeting between start or end
  $q = "SELECT * FROM admin_boardroom_booking "
    . "WHERE NOT (meeting_start BETWEEN '$end' AND '$start' "
    . "OR meeting_end BETWEEN '$end' AND '$start')";
  $result = mysql_query($q);
  // returns true on no conflicts and false elseway
  return mysql_num_rows($result) === 0;
}

Emil Vikström的回答是正确的，但需要考虑一种情况。
例如，其中一个时间范围是另一个时间范围的子集。
因此，假设当满足以下任一条件时，P1{start_time, end_time} 和 P2{start_time, end_time} 将重叠。

P1.start_time <= P2.start_time <= P1.end_time
P1.start_time <= P2.end_time <= P1.end_time
P2.start_time <= P1.start_time <= P1.end_time <= P2.end_time

只是假设时间是按升序排序的。示例如下：

|-----------------------------------|
|  Start time  |   End time  | Name |
|-----------------------------------|
|    10:00     |    14:00    |  P1  |
|-----------------------------------|
|    12:00     |    16:00    |  P2  |
|-----------------------------------|
|    08:00     |    12:00    |  P3  |
|-----------------------------------|
|    07:00     |    16:00    |  P4  |
|-----------------------------------|

如果您将 P1 视为基准时间，并且想对照它检查 P2、P3、P4。

P1.start_time <= P2.start_time <= P1.end_time true
P1.start_time <= P3.end_time <= P1.end_time true
P4.start_time <= P1.start_time <= P1.end_time <= P4.end_time true

通过这种方式，您可以检查是否有任何时间与另一个时间重叠。

如果$to总是晚于 $from 我们可以使用此更短的解决方案

$another_meeting = !($from > $to_compare || $from_compare > $to);

我的解决方案处理边缘情况并且非常紧凑：

    private function meetingOverlap($meeting1, $meeting2){
        if ($meeting1['start']>$meeting2['start'] && $meeting1['start']<$meeting2['end'] ) return true;
        if ($meeting2['start']>$meeting1['start'] && $meeting2['start']<$meeting1['end'] ) return true;
        if ($meeting2['start']==$meeting2['start'] && $meeting1['end']==$meeting2['end'] ) return true;
        return false;
    }