How to resolve the algorithm Pascal's triangle step by step in the PHP programming language

Published on 12 May 2024 09:40 PM

How to resolve the algorithm Pascal's triangle step by step in the PHP programming language

Table of Contents

Problem Statement

Pascal's triangle is an arithmetic and geometric figure often associated with the name of Blaise Pascal, but also studied centuries earlier in India, Persia, China and elsewhere. Its first few rows look like this: where each element of each row is either 1 or the sum of the two elements right above it. For example, the next row of the triangle would be: So the triangle now looks like this: Each row   n   (starting with row   0   at the top) shows the coefficients of the binomial expansion of   (x + y)n.

Write a function that prints out the first   n   rows of the triangle   (with   f(1)   yielding the row consisting of only the element 1). This can be done either by summing elements from the previous rows or using a binary coefficient or combination function. Behavior for   n ≤ 0   does not need to be uniform, but should be noted.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Pascal's triangle step by step in the PHP programming language

1. Pascal's Triangle Function:

  • function pascalsTriangle($num): This function calculates and returns Pascal's triangle up to the specified row number $num.

Implementation:

  • It initializes a variable $c to 1 and an array $triangle to store the triangle.
  • It iterates over the rows from 0 to $num.
  • For each row, it initializes an array to store the coefficients.
  • If the previous row doesn't exist, the first coefficient is set to 1.
  • Otherwise, it calculates each coefficient by combining the values from the previous row.
  • The calculated triangle is returned.

2. tre Function:

  • function tre($n): This function calculates and prints the nth row of Pascal's triangle.

Implementation:

  • It initializes $ck to 1, $kn to $n + 1, and a flag $i to 0.
  • If $kn is even, it divides $kn by 2 and sets $i to 0. Otherwise, it increments $kn and sets $i to 1.
  • It then calculates the coefficients in a loop:
    • It divides $ck by $k times the value ($n-$k+1).
    • It stores the coefficient in an array $arr and prints it on the console.
  • If $kn is greater than 1, it prints the first coefficient of the row and reverses the array $arr.
  • It then iterates over the reversed array and prints the coefficients.

3. Usage:

  • The tre function is used in a loop to print the first 20 rows of Pascal's triangle.
  • The pascalsTriangle function is used to calculate and print the first 8 rows of the triangle.

Overall, this code generates and displays Pascal's triangle using two different methods, each with its own implementation.

Source code in the php programming language

<?php
 //Author Ivan Gavryshin @dcc0
function tre($n) {
  $ck=1;
  $kn=$n+1;
    
 if($kn%2==0) {
 $kn=$kn/2;
 $i=0;
  }
 else
  {

  $kn+=1;
  $kn=$kn/2;
  $i= 1;
}

 for ($k = 1; $k <= $kn-1; $k++) { 
   $ck = $ck/$k*($n-$k+1);
   $arr[] = $ck;
   echo  "+" . $ck ;
 
  }
 

if ($kn>1) {
  echo $arr[i];
  $arr=array_reverse($arr);
 for ($i; $i<= $kn-1; $i++) {
 echo  "+" . $arr[$i]  ;
     }
 
   }
 
 }
 //set amount of strings here
 while ($n<=20) {
 ++$n;
 echo tre($n);
 echo "<br/>";
}
 
 
?>

function pascalsTriangle($num){
	$c = 1;
	$triangle = Array();
	for($i=0;$i<=$num;$i++){
		$triangle[$i] = Array();
		if(!isset($triangle[$i-1])){
			$triangle[$i][] = $c;
		}else{
			for($j=0;$j<count($triangle[$i-1])+1;$j++){
				$triangle[$i][] = (isset($triangle[$i-1][$j-1]) && isset($triangle[$i-1][$j])) ? $triangle[$i-1][$j-1] + $triangle[$i-1][$j] : $c;
			}
		}
	}
	return $triangle;
}

$tria = pascalsTriangle(8);
foreach($tria as $val){
	foreach($val as $value){
		echo $value . ' ';
	}
	echo '<br>';
}

  

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