在我的代码中,我有两个具有相同年龄"Joe"=>"43"
和"Rob"=>"43"
的元素。
我的代码输出是:
乔
我想输出:
Joe和Rob
因为它们具有最高价值。
这是我的代码:
<?php
$cur = 1;
$age = array("Peter" => "35", "Ben" => "37", "Joe" => "43", "Rob" => "43");
$new_array = array();
arsort($age);
$new_array = $age;
$key = array_search(max($new_array), $new_array);
while ($cur > 0) {
echo $key;
$cur--;
}
?>
答案 0 :(得分:12)
我更改了数组中的键和值,然后按键排序并返回第一个键的值:
$ages = array("Peter" => "35", "Ben" => "37", "Joe" => "43", "Rob" => "43");
$new = array();
foreach ($ages as $name => $age) {
$new[$age][] = $name;
}
uksort($new, function($ka, $kb) { return $kb - $ka; }); // or just krsort($new);
$new = array_values($new)[0]; // <- to use this you have to have at least PHP 5.4
// if you have PHP < 5.4 you can simply do it in two steps:
// $new = array_values($new);
// $new = $new[0];
$ages = array("Peter" => "35", "Ben" => "37", "Joe" => "43", "Rob" => "43");
$max = max($ages);
$new = array_keys(array_filter($ages, function ($age) use ($max) { return $age == $max; }));
答案 1 :(得分:10)
使用:
$people = array("Peter" => "35", "Ben" => "37", "Joe" => "43", "Rob" => "43");
$max = max($people);
$result = array_filter($people, function($age) use ($max){ return $max == $age; });
结果是:
Array
(
[Joe] => 43
[Rob] => 43
)
答案 2 :(得分:4)
只需手动检查:
$age = array("Peter" => "35", "Ben" => "37", "Joe" => "43", "Rob" => "43");
$new_array = array();
arsort($age);
$new_array = $age;
$max = max($new_array);
$results = array();
foreach ($new_array as $key => $val) {
if ($val == $max) {
$results[] = $key;
}
}
echo implode(' and ', $results);
// will output "joe and bob"
答案 3 :(得分:4)
我更喜欢@ matteo-tassinari和@evilive的答案,并希望自己提出建议。但是,由于效率问题出现了,这里只有一个循环,因此具有线性时间复杂度:
<?php
$max = ~PHP_INT_MAX;
$result = [];
foreach($age as $key => $value) {
if($value > $max) {
$result = [ $key => $value ];
$max = $value;
}
if($value == $max) {
$result[$key] = $value;
}
}
var_dump($result);
还有另一个使用bucket sort的解决方案:
function bucket($ages) {
$buckets = [];
foreach($ages as $key => $value) {
$buckets[$value][] = $key;
}
return $buckets[max(array_keys($buckets))];
}
关于性能和可伸缩性的讨论,我为四种提议的解决方案(循环,sort,filter,存储桶)编写了一个小的基准脚本:
<?php
function loop($ages) {
$max = 0;
$result = [];
foreach($ages as $key => $value) {
if($value > $max) {
$result = [ $key => $value ];
$max = $value;
}
if($value == $max) {
$result[$key] = $value;
}
}
return array_keys($result);
}
function filter($ages) {
$max = max($ages);
$new = array_filter($ages, function ($age) use ($max) { return $age == $max; });
return array_keys($new);
}
function bucket($ages) {
$buckets = [];
foreach($ages as $key => $value) {
$buckets[$value][] = $key;
}
return $buckets[max(array_keys($buckets))];
}
for($n = 2; $n < 10000000; $n*=2) {
$ages = [];
for($i = 0; $i < $n; $i++) {
$ages['name_'.$i] = rand(0,100);
}
$start = microtime(true);
echo $n.';';
loop($ages);
echo (microtime(true) - $start).';';
$start = microtime(true);
arsort($ages);
echo (microtime(true) - $start).';';
$start = microtime(true);
filter($ages);
echo (microtime(true) - $start).';';
bucket($ages);
echo (microtime(true) - $start).';';
echo PHP_EOL;
}
请仔细检查这是否正确:在命令行中使用php-5.6.15,我的时间看起来像这样:
elements;loop;sort;filter;bucket
...
4096;0.001507;0.009868;0.01211;0.01453;
8192;0.003704;0.002483;0.02488;0.03035;
16384;0.006660;0.01010;0.05396;0.06723;
32768;0.01417;0.01271;0.09163;0.1163;
...
1048576;0.4227;0.9791;2.983;3.943;
2097152;0.8572;2.320;6.064;8.020;
4194304;1.787;4.981;11.90;16.04;
8388608;3.892;10.84;24.76;33.31;
对于少量元素,方法之间的差异并不大,但正如您所看到的,对于最大值,loop
方法比sort
快两倍,快8倍比filter
快bucket
,比loop
快十一倍。因此,如果您的数组是 huge ,则应使用app.get('/user',function(req, res) {
User.find({region: "NA",sector:"Some Sector"}, function(err, user)
{
if (err)
{
res.send(err);
}
console.log(user);
res.json(user);
});
});
。
答案 4 :(得分:3)
您可以使用数组方法 https://stackoverflow.com/a/6153713/217022 和 next 。
使用 next(),您将数组指针移动一个位置。使用键(),您将获得数组指针元素的键。所以最终的代码将是这样的:
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43","Rob"=>"43");
arsort($age);
echo key($age);
next($age);
echo key($age);
key。
答案 5 :(得分:3)
我会做这样的事情
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43","Rob"=>"43");
$max = max($age); //get the highest age
foreach ($age as $key => $value) { //iterate through $age array
if ($value == $max) { //if the value is equal to max age
echo $key."<br />"; // then echo the key
}
}
答案 6 :(得分:1)
我想知道为什么没人使用内置解决方案:
$age = array("Peter"=>"35","Ben"=>"37","Joe"=>"43","Rob"=>"43");
$new = array_keys($input, max($age));
返回 array('Joe','Rob')
https://www.php.net/manual/en/function.array-keys.php说:
array_keys(array $ array,混合$ search_value [,bool $ strict = FALSE]):array
如果指定了search_value,则仅返回该值的键。否则,将返回数组中的所有键。