Question

How to find the max prime number in an array with PHP

Answer 1

function isPrime($n) {
    if ($n == 0) return 0;
    if ($n == 1) return 0;
    for ($i = 2; $i <= sqrt($n); $i++) {
        if ($n % $i == 0)
            return 0;
    }
    return 1;
}


$arr = array(4, 8, 5, 17, 9, 22, 21, 13, 18, 99);
$max = $arr[0];

for ($i = 0; $i < sizeof($arr); $i++) {
      if (isPrime($arr[$i])) { // 5 17 13
          if ($max < $arr[$i]) { 
              $max = $arr[$i];
          } 
      }
}

echo $max;

   
       
/*
run:
            
17
     
*/

 

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