here is the problem, i need to find prime numbers up to a certain number and here is my code:
$a = 56;
for($i = 2; $i<=$a; $i++)
{
if($i == 2)
{
echo "2</br>";
}
if($i == 3)
{
echo "3</br>";
}
if($i == 5)
{
echo "5</br>";
}
if($i == 7)
{
echo "7</br>";
}
for($j =3; $j <= ceil($i/2); $j = $j + 2)
{
if($i % 2 == 0)
{
break;
}
if($i % 3 == 0)
{
break;
}
if($i % 5 == 0)
{
break;
}
if($i % 7 == 0)
{
break;
}
else
{
echo "$i</br>";
break;
}
}
}
It works fine, but it kinda seems like a brute force algorithm, doesnt it? Is there any other way to do this?
Thanks for help!!!
Suppose x is the limit (till which you want prime number)..
for($n=2;$n<=$x;$n++)
{
$i=2;
while($i<=$n-1)
{
if($n % $i == 0)
break;
$i++;
}
if($i==$num)
echo $n; // $n is the prime number...
}
Related
Now the output of the images is carried out using a counter in 3 intervals:
0-73
73-88
88-141
Question: How to remove image output using a counter in the range 0-73?
$name = glob('./album/*.{php}', GLOB_BRACE);
$counter = 0; //заводим счетчик
for($i=0; $i<=(sizeof($name)-1); $i++) {
if( substr($name[$i][2],0,1) != "_") {
echo "<li><img src='".$dir."img/_share/".$shortname."_1.jpg' height='162px'></li>";
$counter++;
if ($counter == 73) {
echo "<li><img src='".$dir."img/_share/".$shortname."_1.jpg' height='162px'></li>";
} elseif ($counter == 88) {
require_once "ddd.php";
} elseif ($counter == 141) {
break;
}
}
}
You need to change == comparison operator to > otherwise it will only execute when $counter is 73. Make sure to remove the extra code that displays the image throughout the loop.
$name = glob('./album/*.{php}', GLOB_BRACE);
$counter = 0; //заводим счетчик
for($i=0; $i<=(sizeof($name)-1); $i++) {
if( substr($name[$i][2],0,1) != "_") {
//echo "<li><img src='".$dir."img/_share/".$shortname."_1.jpg' height='162px'></li>";
$counter++;
if ($counter > 73 && $counter <= 88) {
echo "<li><img src='".$dir."img/_share/".$shortname."_1.jpg' height='162px'></li>";
} elseif ($counter > 88 && $counter <= 141) {
require_once "ddd.php";
} elseif ($counter > 141) {
break;
}
}
}
I'm having trouble making a simple count work. Right now 0 is constantly displayed when I run the code and I know it's because I set count to 0. But it should be displaying the number of times "Fizz" is displayed.
I'm sure it's simple but I just can't see what!
public function __construct($firstParam, $secondParam, $firstSound = "Fizz", $secondSound = "Buzz", $numbers = 100) {
$this->firstParam = $firstParam;
$this->secondParam = $secondParam;
$this->firstSound = $firstSound;
$this->secondSound = $secondSound;
$this->numbers = $numbers;
$this->numsArray = $numsArray;
}
public function __toString() {
$count = 0;
for ($i = 0; $i < count($this->numsArray); $i++){
$val = $this->numsArray[$i];
if ($val == $this->firstSound) {
$count++;
}
}
$print = "Number of Fizzes: ".$count;
return $print;
}
public function execute() {
$this->numsArray = array();
if ($this->secondParam > $this->firstParam) {
for ($i = 1; $i <= $this->numbers; $i++){
if ($i % $this->firstParam == 0 && $i % $this->secondParam == 0) {
$this->numsArray[] = "\n".$this->firstSound.$this->secondSound."\n";
} elseif ($i % $this->firstParam == 0) {
$this->numsArray[] = "\n".$this->firstSound."\n";
} elseif ($i % $this->secondParam == 0) {
$this->numsArray[] = "\n".$this->secondSound."\n";
} else {
$this->numsArray[] = "\n".$i."\n";
}
echo $this->numsArray[$i-1];
}
} else {
echo "\n".' First Number Bigger Than Second '."\n";
}
}
In your execute you are not assigning the values to numsArray[i] also you inject new line characters that will not match the equality you just when checking $val. Also I notice you use zero index to check them and index 1 to load it. Change execute to:
for ($i = 0; $i < $this->numbers; $i++){
if ($i % $this->firstParam == 0 && $i % $this->secondParam == 0) {
$this->numsArray[i] = $this->firstSound.$this->secondSound;
} elseif ($i % $this->firstParam == 0) {
$this->numsArray[i] = $this->firstSound;
} elseif ($i % $this->secondParam == 0) {
$this->numsArray[i] = $this->secondSound;
} else {
$this->numsArray[i] = $i;
}
echo $this->numsArray[$i];
This is a better binary string comparison for php...
if (strcmp($val, $this->firstSound) == 0)
My html document has the following form:
<form action="PrimeNumber.php" method="post">
Enter a number to determine if it is a prime number: <input type="text" name="numb" size="10">
<input type="submit" value="Check for Primeness">
</form>
Edit: Using a different code now but can't get it to echo a statement no matter what I do. Anyone know how I can make it echo is a prime number or is not.
<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
if (isset($_POST['numb'])) {
$num = $_POST['numb'];
function isPrime($num) {
if($num == 1) {
return false;
}
if($num == 2) {
return true;
}
if($num % 2 == 0) {
return false;
}
for($i = 3; $i <= ceil(sqrt($num)); $i = $i + 2) {
if($num % $i == 0)
return false;
}
return true;
}
}
}
?>
simple and easy to understand code, and working as well. do little changes according to your requirement, like assign input text value to $a variable and you good to go.
$a = 51;
for($i=2; $i < $a; $i++){
if($a % $i == 0){
echo "Numberis not prime.";
break;
}
else{
echo "Number is not prime.";
break;
}
}
A simple function to check is prime number:
function is_prime($p) {
return ($p > 1) && (($p%2 >= 1) && ($p%3 >= 1) && ($p%5 >= 1)) || in_array($p, [2,3,5]);
}
function checkPrime($num){
$isPrime = true;
for($i = 2; $i <= sqrt($num); $i++)
{
if($num % $i == 0)
{
$isPrime = false;
}
}
if($isPrime == true)
{
return "$num is prime number";
}else{
return "$num is not prime number";
}
}
echo checkPrime(29);
The output is
29 is prime number
For More Details
You may use the gmp package and correct your code because I got an output as 11 not being a prime number or use the following function as an alternative.
function isPrime($num) {
if($num == 1) {
return false;
}
if($num == 2) {
return true;
}
if($num % 2 == 0) {
return false;
}
for($i = 3; $i <= ceil(sqrt($num)); $i = $i + 2) {
if($num % $i == 0)
return false;
}
return true;
}
More information is available at the following page.
A simple function to help you find out if a number is a prime number
<?php
function fn_prime($number) {
$i = 2; $result = TRUE;
while($i < $number) {
if(!($number%$i)) {
$result = FALSE;
}
$i++;
}
return $result;
}
?>
I'm new to PHP and trying to create the following whilst minimizing the amount of code needed. PHP should show a list of 100 then display if the number is / by 3, 5 or 3 and 5. If not by any then show nothing.
This is what I've got so far, but any help would be great since not sure about the / by 3 and 5 bit as you can see below.
<?php $var = range(0, 100); ?>
<table>
<?php foreach ($var as &$number) {
echo " <tr>
<td>$number</td>
<td>";
if($number % 3 == 0) {
echo "BY3";
} elseif ($number % 5 == 0) {
echo "BY5";
} elseif ($number % 3 and 5 == 0) {
echo "BY3 AND 5";
}
echo "</td></tr>";
}
?>
</table>
Thanks
Nope... you should check first if it's divisble for 15 (3x5) (or 3 and 5) and after you can do other checks:
if($number % 15 == 0) {
echo "BY3 AND 5";
} elseif ($number % 5 == 0) {
echo "BY5";
} elseif ($number % 3 == 0) {
echo "BY3";
}
echo "</td></tr>";
?>
Because every number divisble for 15 is also divisble for 3 and 5. So your last check could never hit
if I'm reading your question correct then you are looking for :
if ($number % 3 == 0 && $number %5 == 0) {
echo "BY3 AND 5";
} elseif ($number % 3 == 0) {
echo "BY3";
} elseif ($number % 5 == 0) {
echo "BY5";
}
Alternative version :
echo ($number % 3 ? ($number % 5 ? "BY3 and 5" : "BY 3") : ($number % 5 ? "BY 5" : ""));
$num_count = 100;
$div_3 = "Divisible by 3";
$div_5 = "Divisible by 5";
$div_both = "Divisible by 3 and 5";
$not_div = "Not Divisible by 3 or 5";
for($i=0;$i<=$num_count;$i++)
{
switch($i)
{
case ($i%15==0):
echo $i." (".$div_both.")</br>";
break;
case ($i%3==0):
echo $i." (".$div_3.")</br>";
break;
case ($i%5==0):
echo $i." (".$div_5.")</br>";
break;
default:
echo $i."</br>";
break;
}
}
No need to do three if statements:
echo "<table border='1'>";
for ($i = 1; $i <= 100; $i++) {
echo "<tr><td>{$i}</td><td>";
if ($i % 3 == 0) echo "BY3 ";
if ($i % 5 == 0) echo "BY5";
echo "</td></tr>\n";
}
echo "</table>";
Update the code as given below
<?php $var = range(0, 100); ?>
<table>
<?php foreach ($var as &$number)
{
echo " <tr>
<td>$number</td>
<td>";
if($number % 3 == 0 && $number % 5 == 0)
{
echo "BY3 AND 5";
}
elseif ($number % 5 == 0)
{
echo "BY5";
}
elseif ($number % 3 == 0)
{
echo "BY3";
}
echo "</td></tr>";
}
?>
<?php
if($number % 5 == 0 && $number % 3 == 0) {
echo "BY3 AND 5";
} elseif ($number % 5 == 0) {
echo "BY5";
} elseif ($number % 3 == 0) {
echo "BY3";
} else{
echo "NOT BY3 OR 5";
}
?>
if($number % 15 == 0)
{
echo "Divisible by 3 and 5";
}
elseif ($number % 5 == 0)
{
echo "Divisible by 5";
}
elseif ($number % 3 == 0)
{
echo "Divisible by 3";
}
This is neater and completed to be run:
<?php
for ($i = 1; $i <= 100; $i++) {
if ($i % 15 == 0)
{
echo"Divisible by 3 and 5</br>";
}
elseif ($i%3==0)
{
echo"Divisible by 3</br>";
}
elseif ($i%5==0)
{
echo"Divisible by 5</br>";
}
else
{
echo $i,"</br>";
}
}
?>
<?php
for ($i = 1; $i <= 100; $i++) {
if ($i % 15 == 0) echo "This Number is Divisible by 3 and 5<br>";
else if ($i % 3 == 0) echo "This Number is Divisible by 3 only<br>";
else if ($i % 5 == 0) echo "This number is Divisible by 5 only<br>";
else{
echo "$i<br>";
}
}
?>
I am just a beginner in PHP. I have tried to write a program for prime numbers, but the result is not correct. I couldn't find the error. How can I correct this? Here is my code:
<?php
$n=15;
for($i=2; $i<=$n; $i++)
{
echo "<br />";
for($j=2; $j<=$i-1; $j++)
{
$k=$i%$j;
if($k==0)
{
break;
}
else echo $i."is prime";
break;
}
}
?>
Try this:
<?php
$n=15;
for($i=2; $i<=$n; $i++)
{
$k = 1; //assume that it is prime
for($j=2; $j<$i; $j++) //if $i is 2, then it won't enter the loop as it will not match the condition ($j<$i)
{
$k=$i%$j;
if($k==0)
break; //if not prime, $k will be set as 0. So, break.
}
if($k!=0) // if $k <> 0, then it is prime
echo "<br />" . $i." is prime";
}
?>
Edit
Updated the code to take care of the "2"
Try this:(whitout using loop)
function is_prime($p) {
return ($p > 1) && (($p%2 >= 1) && ($p%3 >= 1) && ($p%5 >= 1)) || in_array($p, [2,3,5]);
}
echo is_prime(15);
You are breaking the loop the first time it's run by calling this basically:
if (something) {
break;
} else {
break;
}
it will break no matter what. you need to take out the last break.
Well, your code is kind of confusing to understand; at first glance it seems as if it's trying to determine primality by checking every divisor up to N, but you've got that outer-loop going on which I didn't see at first... Oh boy.
If you're just trying to figure out if some number N is prime, the following should work:
$n = 15
$prime = true;
for ($i = 2; $i < sqrt($n); $i++) {
if ($n % $i == 0) {
$prime = false;
break;
}
}
echo $n . " is " . ($prime ? "" : "not") . " prime.";
<?php
echo "TEST\r\n";
$n=15;
for($i=2; $i<=$n; $i++)
{
echo "I= $i \r\n";
for($j=2; $j<=$i-1; $j++)
{
$k = $i%$j;
if($k==0)
{
break;
} else {
echo $i."is prime \r\n";
}
break;
}
}
I think your secod for loop is incorrect.
for($i=2; $i<=$n; $i++) {
echo "<br />";
for($j=2; $j<=$i-1; $j++) {
...
The first value for $j is 2. And for the first time, the first value for $i is 2 again. Now, look at your second for loop code.
It will be like this at the first time:
for($j=2; $j<=2-1; $j++) ... // for($j=2; $j<=1; $j++)
And this condition is not valid at all: 2<=1