How to implement Fibonacci sequence using php

Implementation method: 1. Use array to find, syntax "for($i=0;$i

The operating environment of this tutorial: windows7 system, PHP8 version, DELL G3 computer

Fibonacci numbers are What

Fibonacci sequence, also known as the golden section sequence, because the mathematician Leonardoda Fibonacci used rabbit reproduction as an example It is introduced, so it is also called the "rabbit sequence", which refers to such a sequence:

1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765.......

That is: the first two values ​​​​are both 1, starting from the third digit, each digit is the digit before the current digit. The sum of two digits

In mathematics, the Fibonacci sequence is defined recursively as follows:

F(1)=1，F(2)=1, F(n)=F(n - 1)+F(n - 2)（n ≥ 3，n ∈ N*）

• F: refers to the current sequence

• n: the subscript of the exponential column

Okay, I understand Fiji Bonacci Sequence, let’s take a look at how to implement it using PHP.

Method 1: Use arrays

Observe the sequence given above and combine it with array knowledge to analyze:

• When the array subscript is 0 or 1, the value of the element is 1;
  

• When the array subscript is 2, the element value It is a[0] a[1];

• . When the array index is 3, the element is a[1] a[2];

• ....

• When the array index is n, the element is a[n-2] a [n-1];

can be concluded:

• ##a[0]=1

• a[1]=2

• ##a[n]=a[n-2] a [n-1]

  (n>2)

Code implementation:

<?php
header("Content-type:text/html;charset=utf-8");
function test($num){
    $arr=[];
    for($i=0;$i<$num;$i++)
    {
        if($i==0 || $i==1){
            $arr[$i]=1;
        }else{
            $arr[$i]=$arr[$i-1]+$arr[$i-2];
        }
		echo $arr[$i]." ";
    }
}
echo "斐波那契数列前10位：";
test(10);
echo "<br>斐波那契数列前11位：";
test(11);
echo "<br>斐波那契数列前12位：";
test(12);
?>

Output:

## Now that we understand how to use arrays to find the Fibonacci sequence, let's take a look at using recursion to find the Fibonacci sequence.

Method 2: Using recursion

<?php
header("Content-type:text/html;charset=utf-8");
function fbnq($n) {
	if ($n <= 0) {
		return 0;
	}
	if ($n == 1 || $n == 2) {
		return 1;
	}
	return fbnq($n - 1) + fbnq($n - 2);
}

echo "斐波那契数列第10位：" . fbnq(10);
echo "<br>斐波那契数列第11位：" . fbnq(11);
echo "<br>斐波那契数列第12位：" . fbnq(12);
?>

Output:

The recursive method has also been implemented, isn’t it very simple!

The recursive algorithm can solve a responsible problem using shorter code, but its operation efficiency is relatively low.

Recommended learning: "

PHP Video Tutorial

"

The above is the detailed content of How to implement Fibonacci sequence using php. For more information, please follow other related articles on the PHP Chinese website!