Sé que este es un hilo de mensajes antiguos, pero incluyo mi prueba PHP personal de la idea SKIP/TAKE que encontré aquí. Estoy llamando al mío STEP (+)/SPAN (-). Quizás alguien lo encuentre útil.
NOTA: Implementé la capacidad de permitir enteros duplicados así como enteros negativos aunque la pregunta original incluía enteros positivos, no duplicados. Siéntete libre de ajustarlo si quieres intentar afeitar un byte o dos.
CÓDIGO:
// $integers_array can contain any integers; no floating point, please. Duplicates okay.
$integers_array = [118, 68, -9, 82, 67, -36, 15, 27, 26, 138, 45, 121, 72, 63, 73, -35,
68, 46, 37, -28, -12, 42, 101, 21, 35, 100, 44, 13, 125, 142, 36, 88,
113, -40, 40, -25, 116, -21, 123, -10, 43, 130, 7, 39, 69, 102, 24,
75, 64, 127, 109, 38, 41, -23, 21, -21, 101, 138, 51, 4, 93, -29, -13];
// Order from least to greatest... This routine does NOT save original order of integers.
sort($integers_array, SORT_NUMERIC);
// Start with the least value... NOTE: This removes the first value from the array.
$start = $current = array_shift($integers_array);
// This caps the end of the array, so we can easily get the last step or span value.
array_push($integers_array, $start - 1);
// Create the compressed array...
$compressed_array = [$start];
foreach ($integers_array as $next_value) {
// Range of $current to $next_value is our "skip" range. I call it a "step" instead.
$step = $next_value - $current;
if ($step == 1) {
// Took a single step, wait to find the end of a series of seqential numbers.
$current = $next_value;
} else {
// Range of $start to $current is our "take" range. I call it a "span" instead.
$span = $current - $start;
// If $span is positive, use "negative" to identify these as sequential numbers.
if ($span > 0) array_push($compressed_array, -$span);
// If $step is positive, move forward. If $step is zero, the number is duplicate.
if ($step >= 0) array_push($compressed_array, $step);
// In any case, we are resetting our start of potentialy sequential numbers.
$start = $current = $next_value;
}
}
// OPTIONAL: The following code attempts to compress things further in a variety of ways.
// A quick check to see what pack size we can use.
$largest_integer = max(max($compressed_array),-min($compressed_array));
if ($largest_integer < pow(2,7)) $pack_size = 'c';
elseif ($largest_integer < pow(2,15)) $pack_size = 's';
elseif ($largest_integer < pow(2,31)) $pack_size = 'l';
elseif ($largest_integer < pow(2,63)) $pack_size = 'q';
else die('Too freaking large, try something else!');
// NOTE: I did not implement the MSB feature mentioned by Marc Gravell.
// I'm just pre-pending the $pack_size as the first byte, so I know how to unpack it.
$packed_string = $pack_size;
// Save compressed array to compressed string and binary packed string.
$compressed_string = '';
foreach ($compressed_array as $value) {
$compressed_string .= ($value < 0) ? $value : '+'.$value;
$packed_string .= pack($pack_size, $value);
}
// We can possibly compress it more with gzip if there are lots of similar values.
$gz_string = gzcompress($packed_string);
// These were all just size tests I left in for you.
$base64_string = base64_encode($packed_string);
$gz64_string = base64_encode($gz_string);
$compressed_string = trim($compressed_string,'+'); // Don't need leading '+'.
echo "<hr>\nOriginal Array has "
.count($integers_array)
.' elements: {not showing, since I modified the original array directly}';
echo "<br>\nCompressed Array has "
.count($compressed_array).' elements: '
.implode(', ',$compressed_array);
echo "<br>\nCompressed String has "
.strlen($compressed_string).' characters: '
.$compressed_string;
echo "<br>\nPacked String has "
.strlen($packed_string).' (some probably not printable) characters: '
.$packed_string;
echo "<br>\nBase64 String has "
.strlen($base64_string).' (all printable) characters: '
.$base64_string;
echo "<br>\nGZipped String has "
.strlen($gz_string).' (some probably not printable) characters: '
.$gz_string;
echo "<br>\nBase64 of GZipped String has "
.strlen($gz64_string).' (all printable) characters: '
.$gz64_string;
// NOTICE: The following code reverses the process, starting form the $compressed_array.
// The first value is always the starting value.
$current_value = array_shift($compressed_array);
$uncompressed_array = [$current_value];
foreach ($compressed_array as $val) {
if ($val < -1) {
// For ranges that span more than two values, we have to fill in the values.
$range = range($current_value + 1, $current_value - $val - 1);
$uncompressed_array = array_merge($uncompressed_array, $range);
}
// Add the step value to the $current_value
$current_value += abs($val);
// Add the newly-determined $current_value to our list. If $val==0, it is a repeat!
array_push($uncompressed_array, $current_value);
}
// Display the uncompressed array.
echo "<hr>Reconstituted Array has "
.count($uncompressed_array).' elements: '
.implode(', ',$uncompressed_array).
'<hr>';
SALIDA:
--------------------------------------------------------------------------------
Original Array has 63 elements: {not showing, since I modified the original array directly}
Compressed Array has 53 elements: -40, 4, -1, 6, -1, 3, 2, 2, 0, 8, -1, 2, -1, 13, 3, 6, 2, 6, 0, 3, 2, -1, 8, -11, 5, 12, -1, 3, -1, 0, -1, 3, -1, 2, 7, 6, 5, 7, -1, 0, -1, 7, 4, 3, 2, 3, 2, 2, 2, 3, 8, 0, 4
Compressed String has 110 characters: -40+4-1+6-1+3+2+2+0+8-1+2-1+13+3+6+2+6+0+3+2-1+8-11+5+12-1+3-1+0-1+3-1+2+7+6+5+7-1+0-1+7+4+3+2+3+2+2+2+3+8+0+4
Packed String has 54 (some probably not printable) characters: cØÿÿÿÿ ÿõ ÿÿÿÿÿÿ
Base64 String has 72 (all printable) characters: Y9gE/wb/AwICAAj/Av8NAwYCBgADAv8I9QUM/wP/AP8D/wIHBgUH/wD/BwQDAgMCAgIDCAAE
GZipped String has 53 (some probably not printable) characters: xœ Ê» ÑÈί€)YšE¨MŠ“^qçºR¬m&Òõ‹%Ê&TFʉùÀ6ÿÁÁ Æ
Base64 of GZipped String has 72 (all printable) characters: eJwNyrsNACAMA9HIzq+AKVmaRahNipNecee6UgSsBW0m0gj1iyXKJlRGjcqJ+cA2/8HBDcY=
--------------------------------------------------------------------------------
Reconstituted Array has 63 elements: -40, -36, -35, -29, -28, -25, -23, -21, -21, -13, -12, -10, -9, 4, 7, 13, 15, 21, 21, 24, 26, 27, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 51, 63, 64, 67, 68, 68, 69, 72, 73, 75, 82, 88, 93, 100, 101, 101, 102, 109, 113, 116, 118, 121, 123, 125, 127, 130, 138, 138, 142
--------------------------------------------------------------------------------
¿Quizás obtendría mejores respuestas si proporcionara un conjunto de datos de muestra real/mayor? – conny
bueno, aquí hay uno para pensar en los datos - int [] data; for (int i = 0; i
pdeva
Ya ha proporcionado una buena compresión en la forma en que describe su secuencia aquí – sbeliakov