如何降低范围名单？ [英] How to reduce lists of ranges?

问题描述

给定范围的名单，即： 1-3,5,6-4,31,9,19,10,25-20 我怎样才能将其降低到 1-6,9-10,19-25,31 ？

Given a list of ranges ie: 1-3,5,6-4,31,9,19,10,25-20 how can i reduce it to 1-6,9-10,19-25,31 ?

下面是我到目前为止已经做了，似乎有点复杂，所以 有没有更简单的/聪明的方法来做到这一点。

Here is what i've done so far, it seems a little bit complicated, so is there any simpler/clever method to do this.

$in = '1-3,5,6-4,31,9,19,10,25-20';
// Explode the list in ranges
$rs = explode(',', $in);
$tmp = array();
// for each range of the list
foreach($rs as $r) {
    // find the start and end date of the range
    if (preg_match('/(\d+)-(\d+)/', $r, $m)) {
        $start = $m[1];
        $end = $m[2];
    } else {
        // If only one date
        $start = $end = $r;
    }
    // flag each date in an array
    foreach(range($start,$end) as $i) {
        $tmp[$i] = 1;
    }
}
$str = '';
$prev = 999;
// for each date of a month (1-31)
for($i=1; $i<32; $i++) {
    // is this date flaged ?
    if (isset($tmp[$i])) {
        // is output string empty ?
        if ($str == '') {
            $str = $i;
        } else {
            // if the previous date is less than the current minus 1
            if ($i-1 > $prev) {
                // build the new range
                $str .= '-'.$prev.','.$i;
            }
        }
        $prev = $i;
    }
}
// build the last range
if ($i-1 > $prev) {
    $str .= '-'.$prev;
}
echo "str=$str\n";

注：必须在PHP 5.1.6运行（我不能升级）

NB: it must run under php 5.1.6 (i can't upgrade).

仅供参考：再一个月present天数，使他们被限制在1-31

FYI : the numbers represent days of month so they are limited to 1-31.

从日期（1-3,6,7-8），我想重新获取列表（1-给定范围内3,6-8），所有的范围被重新计算，并下令。

From a given range of dates (1-3,6,7-8), i'd like obtain another list (1-3,6-8) where all the ranges are recalculated and ordered.

推荐答案

也许不是最有效的，但不应该是太糟糕了你正在使用的值的有限范围：

Perhaps not the most efficient, but shouldn't be too bad with the limited range of values you're working with:

$in = '1-3,5,6-4,31,9,19,10,25-20';

$inSets = explode(',',$in);
$outSets = array();
foreach($inSets as $inSet) {
    list($start,$end) = explode('-',$inSet.'-'.$inSet);
    $outSets = array_merge($outSets,range($start,$end));
}
$outSets = array_unique($outSets);
sort($outSets);

$newSets = array();
$start = $outSets[0];
$end = -1;
foreach($outSets as $outSet) {
    if ($outSet == $end+1) {
        $end = $outSet;
    } else {
        if ($start == $end) {
            $newSets[] = $start;
        } elseif($end > 0) {
            $newSets[] = $start.'-'.$end;
        }
        $start = $end = $outSet;
    }
}
if ($start == $end) {
    $newSets[] = $start;
} else {
    $newSets[] = $start.'-'.$end;
}
var_dump($newSets);
echo '<br />';

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