我想查找數組中第二高的變量。查找數組中第二高的變量
例如，如果我有：
$cookies = array(
"chocolate" => "20",
"vanilla" => "14",
"strawberry" => "18",
"raspberry" => "19",
"bluebery" => "29"
);
我可以使用max($cookies)找到最高的變量，這是"bluebery" => "29"。
但是，如何找到第二高？"chocolate" => "20"
排序，並得到第二項是最簡單的方法：
arsort($cookies);
$keys = array_keys($cookies);
echo $keys[1]; // chocolate
echo $cookies[$keys[1]]; // 20
如果你想要一個更有效的方法，你也可以做手工，通過保持雙方最高和第二高的項目的跟蹤在同一時間：
function secondMax($arr) {
$max = $second = 0;
$maxKey = $secondKey = null;
foreach($arr as $key => $value) {
if($value > $max) {
$second = $max;
$secondKey = $maxKey;
$max = $value;
$maxKey = $key;
} elseif($value > $second) {
$second = $value;
$secondKey = $key;
}
}
return array($secondKey, $second);
}
用法：
$second = secondMax($cookies);
echo "{$second[0]} => {$second[1]}"; // chocolate => 20
排序陣列降，並採取第第二個價值。或者，爲了保存，取第一個值並遍歷數組，直到找到一個較小的值。
嘗試：
asort($cookies);
end($cookies);
prev($cookies);
list($key,$value) = each($cookies);
或扭轉它
arsort($cookies);
reset($cookies);
next($cookies);
list($key,$value) = each($cookies);
** 編輯 **
我想我反正分享這個，如果有人碰到這個跌跌需要它：
/**
* Returns the key => value pair with the specific rank.
* if $rank is 0, falase is returned. If $rank is positive,
* then the $rank th smallest pair is returned. If $rank
* is negative, then the $rank th biggest pair is returned.
* If $rank range is outside the size of the array, false
* is returned. If a callable function is provided, it will
* be used to sort the data. If $keySort is true, then the
* data will be sorted by keys instead (the callback functions
* will receive the keys to compare instead of values)
*
* @param $data array
* @param $rank int
* @param $cmd_function callable (optional)
* @param $keySort boolean (optional)
* @return array the key => value pair or false
*/
function findByRank($data, $rank, $cmd_function = null, $keySort = false) {
if (($rank == 0) || (abs($rank) > count($data))) {
return false;
}
$sort = ($keySort?'k':'a').'sort';
if ($cmd_function != null) {
$sort = 'u'.$sort;
$sort($data, $cmd_function);
} else {
$sort($data);
}
if ($rank > 0) {
reset($data);
$next = 'next';
} else {
end($data);
$next = 'prev';
$rank = abs($rank);
}
while (--$rank > 0) $next($data);
return each($data);
}
$cookies = array(
"chocolate" => "20",
"vanilla" => "14",
"strawberry" => "18",
"raspberry" => "19",
"bluebery" => "29"
);
header('Content-type:text/plain; charset=utf-8');
var_dump(findByRank($cookies, -10)); // -> false
var_dump(findByRank($cookies, -2)); // -> 'chocolate' key=>value pair
var_dump(findByRank($cookies, -1)); // -> 'blueberry' key=>value pair
var_dump(findByRank($cookies, 0)); // -> false
var_dump(findByRank($cookies, 1)); // -> 'vanilla' key=>value pair
var_dump(findByRank($cookies, 3)); // -> 'raspberry' key=>value pair
'ksort'按鍵排序。你的意思是'asort'嗎？ – Ryan
哎呀，是的，我在想「排序保存鍵聯合」，但'asort'是正確的功能，是的 –
rsort($cookies);
echo $cookies[1];
你不能拿到鑰匙。 –
arsort($cookies) AND array_shift($cookies) AND list($k, $v) = each($cookies);
echo "$k => $v"; // chocolate => 20
非常感謝!!!!!!!!!! – supercoolville
檢查該URL
http://maheshbokkisam.blogspot.in/2013/04/find-nth-highest-value-in-array-without.html
查找給定陣列第N/N個最高值，而無需使用任何排序在PHP
$ar = array(23,56,87,12,98,85,24,54,99,100,1,4,5,2,76,37,92);
$n = count($ar) - 5;
for($i = 0; $i < $n; $i++){
// Get the max value from array // get the Nth value from last loop
echo $a = max($ar);
echo "<br /><pre>"; print_r($ar);
$ar = array_flip($ar); // Flip the array
//print_r($ar);
unset($ar[$a]); // Unset the max value from array
//print_r($ar);
$ar = array_flip($ar); // Flip the array
echo "</pre>";
echo "<hr />";
}
function second_largest($arr)
{
sort($arr, SORT_NUMERIC);
return($arr[count($arr) - 2]);
}
//echo 3
echo second_largest(array(0, 3, 4, 1, 2));
<?php
// Finding Second highest number (In case of index of array is random)
$arr = [-5 => 33, -4 => -2, 8 => 0, 44, 44, 44, 44, 44];
$max = -INF;
$secondMax = -INF;
$size = sizeof($arr);
if ($size > 1) {
foreach ($arr as $key => $value) {
echo "KEY-> ", $key, "VALUE->", $value, "\n";
if ($value > $max) {
$max = $value;
} else {
if ($value < $max && $value > $secondMax) {
$secondMax = $value;
}
}
}
} else if ($size == 0) {
$max = "No Max element";
$secondMax = "No Second highest element";
} else {
foreach ($arr as $key => $value) {
$max = $arr[$key];
$secondMax = "No second highest element";
}
}
echo "maxvalue = ", $max, "\n";
echo "secondmax =", $secondMax;
選項一：從陣列中刪除最大元素並再次查找最大值。第二：排列數組並取第二個元素。 – Leri
你嘗試過什麼方法？想到一對夫婦的想法：你可以穿過陣列並選出最高的兩個，類似於選擇較高的一個。另一個是你可以挑選第二個。 – GreenMatt