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PHP for loop Exercises: Generate and display the first n lines of a Floyd triangle

PHP for loop: Exercise-12 with Solution

Write a PHP program to generate and display the first n lines of a Floyd triangle. (use n=5 and n=11 rows).

According to Wikipedia Floyd's triangle is a right-angled triangular array of natural numbers, used in computer science education. It is named after Robert Floyd. It is defined by filling the rows of the triangle with consecutive numbers, starting with a 1 in the top left corner:

Pictorial Presentation:

PHP for loop Exercises: Generate and display the first n lines of a Floyd triangle

Sample Solution:

PHP Code:

<?php
$n = 5; 
echo "n = " . $n . "\n";
$count = 1;
for ($i = $n; $i > 0; $i--) 
{
  for ($j = $i; $j < $n + 1; $j++) 
   {
     printf("%4s", $count);
     $count++;
   } 
	echo "\n";
   }
?>

Sample Output: 

n = 5                                                       
   1                                                        
   2   3                                                    
   4   5   6                                                
   7   8   9  10                                            
  11  12  13  14  15

Flowchart:

Flowchart: Generate and display the first n lines of a Floyd triangle

PHP Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Write a PHP program which iterates the integers from 1 to 100. For multiples of three print "Fizz" instead of the number and for the multiples of five print "Buzz". For numbers which are multiples of both three and five print "FizzBuzz".
Next: Write a PHP program to print alphabet pattern 'A'.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



PHP: Tips of the Day

How to Sort Multi-dimensional Array by Value?

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

Example:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Ref : https://bit.ly/3i77vCC