PHP Full permutation algorithm Implementation program code _php tutorial

PHP Full permutation algorithm Implementation program code

Any element of M (m≤n) from n different elements, arranged in a certain order, is called an arrangement of extracting m elements from n different elements. All permutations are called when m=n.

Brief introduction

The full arrangement of three elements such as the three-in-one is:

The

1,3,2

2,1,3

2,3,1

3,1,2

3,2,1

Total 3*2*1=6 species 3!

2 formula

Number of full permutations f (n) =n! (Definition 0!=1)

Recursive algorithm

The

1,3,2

2,1,3

2,3,1

3,2,1

3,1,2

This is because the algorithm only takes into account how the output is fully aligned, regardless of whether there is a problem with the transposition. So I proposed the solution, that is, the transposition function modified under

such as 1 2 3 transposition, should not be directly 3 2 1 so that 3 and 1 direct transposition; Instead, let the 3 rank at the front and back, 1 2 backwards.

Basic algorithms

The following is a description of the total permutation algorithm four:

(A) Dictionary ordering method

(B) Increment of rounding method

(C) Descending rounding Method

(D) adjacent position swap method

Implementing a full permutation algorithm

The code is as follows

Header ("Content-type:text/html;charset=utf-8");/** * @param array $a the set of elements to be arranged, will change dynamically * @param array $b storage current arrangement * @param array $M The set of elements to be arranged, equivalent to a constant, always the initial set of elements to be arranged */ function Wholerange ($a, $b, $M) { $range =array (); if (count ($a) > 1) { $d = $b; foreach ($a as $value) { $b []= $value; $c =array_diff ($M, $b); if (count ($c) > 0) { $range []=wholerange ($c, $b, $M); } $b = $d; } }elseif (count ($a) = = 1) { foreach ($a as $value) { $b []= $value; } $onerange = ""; foreach ($b as $value) { $onerange. = $value; } $range []= $onerange; } return $range; } /** * Recursive output array * * @param array $arr to be output * @return Int returns the number of array elements */ function Recursionarray ($arr) { $i = 0; foreach ($arr as $value) { if (Is_array ($value)) { $i +=recursionarray ($value); }else{ echo $value. " "; $i + +; } } return $i; } $a =array (' A ', ' B ', ' C ', ' D '); $b =array (); $range =wholerange ($a, $b, $a); $count =recursionarray ($range); echo "A total of". $count. " Arrangement "; ?>

http://www.bkjia.com/PHPjc/941716.html www.bkjia.com true http://www.bkjia.com/PHPjc/941716.html techarticle The PHP full permutation algorithm implements code that takes M (MN) elements from n different elements, arranged in a certain order, and is called an arrangement of extracting m elements from n different elements. When ...

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