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PHP Exercises: Print the number of prime numbers which are less than or equal to a given integer

PHP: Exercise-52 with Solution

Write a PHP program to print the number of prime numbers which are less than or equal to a given integer.

Input:
n (1 ≤ n ≤ 999,999) .

Pictorial Presentation:

PHP: Print the number of prime numbers which are less than or equal to a given integer.

Sample Solution: -

PHP Code:

<?php

$a = array_fill(0, 1000000, true);
$a[0] = $a[1] = false;
 
for($i = 2; $i * $i < 1000000; $i++){
    if(!$a[$i]) continue;
    for($j = $i * $i; $j < 1000000; $j += $i){
        $a[$j] = false;
    }
}
 
$sum = array_fill(0, 1000000, 0);
 
for($i = 1; $i < 1000000; $i++){
    $sum[$i] += $sum[$i - 1];
    if($a[$i]) $sum[$i]++;
}
 
while(fscanf(STDIN, "%d", $n)){
    echo "Number of prime numbers which are less than or equal to n: ";
    echo $sum[$n] . "\n";
}
?>

Sample Output: 

Sample Input: 50
Number of prime numbers which are less than or equal to n: 15

Flowchart:

Flowchart: Print the number of prime numbers which are less than or equal to a given integer.

PHP Code Editor:

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Next: Write a PHP program to compute the radius and the central coordinate (x, y) of a circle which is constructed by three given points on the plane surface.

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PHP: Tips of the Day

Mutates the original array to filter out the values specified

Example:

<?php
function tips_pull(&$items, ...$params)
{
  $items = array_values(array_diff($items, $params));
  return $items;
}

$items = ['x', 'y', 'z', 'x', 'y', 'z'];
print_r(tips_pull($items, 'y', 'z'));
?>

Output:

Array
(
    [0] => x
    [1] => x
)