PHP greedy algorithm solves 0-1 knapsack problem case Analysis _php Tutorial

PHP greedy algorithm solves 0-1 knapsack problem case Analysis

This article mainly introduces the PHP greedy algorithm solves 0-1 knapsack problem, the example analyzes the greedy algorithm principle and the knapsack problem realization skill, needs the friend to refer to the next

This article describes the PHP greedy algorithm to solve the 0-1 knapsack problem method. Share to everyone for your reference. The specific analysis is as follows:

Greedy algorithm solves 0-1 knapsack problem, the global optimal solution is obtained by local optimal solution! More flexible than dynamic planning to solve knapsack problems!

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0-1 knapsack greedy algorithm problem Class tanxin{ Public $weight; Public $price; Public function __construct ($weight =0, $price =0) { $this->weight= $weight; $this->price= $price; } } Generate Data $n = 10; for ($i =1; $i <= $n; $i + +) { $weight =rand (1,20); $price =rand (1,10); $x [$i]=new tanxin ($weight, $price); } Output results function display ($x) { $len =count ($x); foreach ($x as $val) { echo $val->weight, ", $val->price; Echo ' '; } } Sort by price and weight ratio Function Tsort (& $x) { $len =count ($x); for ($i =1; $i <= $len; $i + +) { for ($j =1; $j <= $len-$i; $j + +) { $temp = $x [$j]; $res = $x [$j +1]->price/$x [$j +1]->weight; $temres = $temp->price/$temp->weight; if ($res > $temres) { $x [$j]= $x [$j +1]; $x [$j +1]= $temp; } } } } Greedy algorithm function Tanxin ($x, $totalweight =50) { $len =count ($x); $allprice = 0; for ($i =1; $i <= $len; $i + +) { if ($x [$i]->weight> $totalweight) break; else{ $allprice + = $x [$i]->price; $totalweight = $totalweight-$x [$i]->weight; } } if ($i < $len) $allprice + = $x [$i]->price* ($totalweight/$x [$i]->weight); return $allprice; } Tsort ($x);//Sort by non-ascending order Display ($x);//Show The best solution for Echo ' 0-1 backpack is: '; echo tanxin ($x);

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