how to find highest and second highest number in an array without using max function

Question

I already have solution. But i think it will be more optimizable. So please provide me a solution for it. And remember that don't use predefined function of php. Like max() function. i know there are so many ways to find it but i want best and better solution. Because my array contains more than 1 lakh records and it's taking lot of time. Or sometime site will be down.

My code :

<?php 

$array = array('1', '15', '2','10',4);

echo "<pre>";
print_r($array);
echo "<pre>";
$max = 0;
$s_max=0;

for($i=0; $i<count($array); $i++)
{
    $a = $array[$i];
    $tmax = $max;
    $ts_max = $s_max;
    if($a > $tmax && $a > $ts_max)
    {
        $max = $a;
        if($tmax > $ts_max) {
            $s_max = $tmax;
        } else {
            $s_max = $ts_max;
        }
    } else if($tmax > $a && $tmax > $ts_max)
    {
        $max = $tmax;
        if($a > $ts_max) {
            $s_max = $a;
        } else {
            $s_max = $ts_max;
        }
    } else if($ts_max > $a && $ts_max > $tmax)
    {
        $max = $ts_max;
        if($a > $tmax)
        {
            $s_max = $a;
        } else {
            $s_max = $tmax;
        }
    }
}
echo "Max=".$max;
    echo "<br />";
    echo "S_max=".$s_max;
    echo "<br />";

?>

Answer 1

<?php 
$array = array('200', '15','69','122','50','201');
$max_1 = $max_2 = 0;

for ($i=0; $i<count($array); $i++) {
    if ($array[$i] > $max_1) {
      $max_2 = $max_1;
      $max_1 = $array[$i];
    } else if ($array[$i] > $max_2 && $array[$i] != $max_2) {
      $max_2 = $array[$i];
    }
}
echo "Max=".$max_1;
echo "<br />"; 
echo "Smax 2=".$max_2;

Answer 2

See this solution.

<?php 

 $numbers = array_unique(array(1,15,2,10,4)); 
// rsort : sorts an array in reverse order (highest to lowest).

 rsort($numbers); 

 echo 'Highest is -'.$numbers[0].', Second highest is -'.$numbers[1];

 // O/P: Highest is -15, Second highest is -10
 ?>

Answer 3

I didn't check your solution, but in terms of complexity it's IMO optimal. If the array has no more structural information (like it's sorted) there's no way to skip entries. I.e. the best solution is in O(n) which your solution is.

Answer 4

This is a perfect and shortest code to find out the second largest value from the array. The below code will always return values in case the array contains only a value.

Example 1.
    $arr = [5, 8, 1, 9, 24, 14, 36, 25, 78, 15, 37];
    asort($arr);
    $secondLargestVal = $arr[count($arr)-1];

    //this will return 37

Example 2.

    $arr = [5];
    asort($arr);
    $secondLargestVal = $arr[count($arr)-1];
    //this will return 5

Answer 5

The answer given by "Kanishka Panamaldeniya" is fine for highest value but will fail on second highest value i.e. if array has 2-similar highest value, then it will showing both Highest and second highest value same. I have sorted out it by adding one more level comparsion and it works fine.

$array = array(50,250,30,250,40,70,10,50); // 250  2-times
$max=$max2=0;
for ($i = 0; $i < count($array); $i++) {
if ($array[$i] > $max) {
    $max2 = $max;
    $max = $array[$i];
} else if (($array[$i] > $max2) && ($array[$i] != $max)) {
    $max2 = $array[$i];
}
}
echo "Highest Value is : " . $max . "<br/>"; //output : 250
echo "Second highest value is : " . $max2 . "<br/>"; //output : 70

Answer 6

$array = array(80,250,30,40,90,10,50,60,50);            // 250  2-times
$max=$max2=0;

foreach ($array as $key =>$val) {

    if($max < $val) {
        $max2 =$max;
        $max = $val;        
    }

    elseif(($max2 < $val) && ($max!=$val) {
        $max2 = $val;
    }
}

echo "Highest Value is : " . $max . "<br/>";           //output: 250
echo "Second highest value is : " . $max2 . "<br/>";   //output: 90

Answer 7

This code will return second max value from array

$array = array(80,250,30,250,40,90,10,50,60,50); // 250  2-times
$max=$max2=0;

for ($i = 0; $i < count($array); $i++) {
    if($i == 0) {
        $max2 = $array[$i];
    }
     
    if($array[$i] > $max) {
        $max = $array[$i];
    }
    
    if($max > $array[$i] && $array[$i] > $max2) {
        $max2 = $array[$i];
    }
}    


echo "Highest Value is : " . $max . "<br/>"; //output : 250
echo "Second highest value is : " . $max2 . "<br/>"; //output : 90

Answer 8

You can also use techniques in sorting like Bubble sort

function bubble_Sort($my_array )
{
    do
    {
        $swapped = false;
        for( $i = 0, $c = count( $my_array ) - 1; $i < $c; $i++ )
        {
            if( $my_array[$i] > $my_array[$i + 1] )
            {
                list( $my_array[$i + 1], $my_array[$i] ) =
                        array( $my_array[$i], $my_array[$i + 1] );
                $swapped = true;
            }
        }
    }
    while( $swapped );
return $my_array;
}

$test_array = array(3, 0, 2, 5, -1, 4, 1);
echo "Original Array :\n";
echo implode(', ',$test_array );
echo "\nSorted Array\n:";
echo implode(', ',bubble_Sort($test_array)). PHP_EOL;

Original Array :                                                    
3, 0, 2, 5, -1, 4, 1                                                
Sorted Array :                                                      
-1, 0, 1, 2, 3, 4, 5

Flow explanation

Answer 9

See this solution, PHP find second largest element in given array without built-in sort function

<?php

function secondLargest($array){
    for($i=0; $i<count($array); $i++){
        for($j=0; $j<count($array)-1; $j++){
            if($array[$j] > $array[$j+1]){
            $temp = $array[$j+1];
            $array[$j+1] = $array[$j];
            $array[$j] = $temp;
            }
        }
    }
  return $array[sizeof($array)-2];
}

$arr = [-1, 8, 4, 2, 8];
print_r(secondLargest($arr));
?>