get min and max position in array where value exist - php

Question

I need to find the min and max position into an array where some value exist!
use a loop inside a loop to compare values is not an option ( my array has 100.000 values )
e.g=
$myarray[0]="red";
$myarray[1]="red";
$myarray[2]="blue";
$myarray[3]="blue";
$myarray[4]="blue";
$myarray[5]="red";
how to get the min and max position where blue exist?

Answer 1

Use the second argument for array_keys:
if($blue = array_keys($myarray, 'blue')) {
$min = min($blue);
$max = max($blue);
}

Answer 2

may be this is the answer?
function getMinKey($arr, $search){
if(!in_array($search, $arr)){
return false;
}
foreach($arr as $key => $value){
if($value == $search){
return $key;
}
}
}
function getMaxKey($arr, $search){
if(!in_array($search, $arr)){
return false;
}
$arrCount = count($arr)-1;
for($i = $arrCount; $i >=0; $i--){
if($arr[$i] == $search){
return $i;
}
}
}

Answer 3

All solutions, so far, have searched the whole array, which might be quite inefficient. You only need to search from the start upto the first "blue" and from the end downto the last "blue". Like this:
$find = "blue";
$first = false;
$last = false;
$max = count($myarray);
$key = 0;
while ($key < $max) {
if ($myarray[$key] == $find) {
$first = $key;
break;
}
$key++;
}
if ($first !== false) {
$key = --$max;
while ($key > 0) {
if ($myarray[$key] == $find) {
$last = $key;
break;
}
$key--;
}
}
Note that this code takes into account that nothing will be found. In that case $first and $last will contain false. It also checks to see if the $first was found to prevent searching through the array twice when there's clearly no need for that.

Answer 4

You can use array_keys with the search_value to extract all the matching keys, and then max and min to get the two ones that you want.
$keys = array_keys($myarray,'blue'); //[2,3,4]
$maxKey = max($keys); //4
$minKey = min($keys); //2
I have to advise that performance wise is better to do a for loop:
$length = count($myarray);
$minKey = FALSE;
$maxKey = FALSE;
$search = 'blue';
for($i=0;$i<$length;$i++){
if($myarray[$i] == $search){
if($minKey === FALSE) $minKey = $i;
$maxKey = $i;
}
}