Question

How to find first and last positions of an element in a sorted array in PHP

Answer 1

function find_first_and_Last_position($arr, $n) { 
    $first = -1; $last = -1; 
     
    for ($i = 0; $i < count($arr); $i++) { 
        if ($n != $arr[$i]) 
            continue; 
        if ($first == -1) 
            $first = $i; 
        $last = $i; 
    } 
    if ($first != -1) 
        echo "First positions = " . $first . " Last positions = " . $last; 
    else
        echo "Not Found"; 
} 
   
 
$arr = array(1, 3, 7, 8, 3, 1, 9); 
$n = 3; 
       
find_first_and_Last_position($arr, $n); 
      
 
  
    
/*
run:
         
First positions = 1 Last positions = 4
  
*/

 

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Answer 2

function find_first_and_Last_position($arr, $n, &$first, &$last) { 
    for ( $i = 0; $i < count($arr); $i++) { 
        if ($n != $arr[$i]) 
            continue; 
        if ($first == -1) 
            $first = $i; 
        $last = $i; 
    } 
} 
   
 
$arr = array(1, 3, 7, 8, 3, 1, 9); 
$n = 3; 
$first = -1;
$last = -1;
       
find_first_and_Last_position($arr, $n, $first, $last); 
 
if ($first != -1) 
    echo "First positions = " . $first . " Last positions = " . $last; 
else
    echo "Not Found"; 
      
 
 
    
/*
run:
         
First positions = 1 Last positions = 4
  
*/

 

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