PHP Backtracking method solves 0-1 knapsack problem case Analysis _php Tutorial

A case study of 0-1 knapsack problem solved by PHP backtracking

This article mainly introduced the PHP backtracking method solves 0-1 knapsack problem, the example analyzes the PHP backtracking method solves the knapsack question the skill, has the certain reference value, needs the friend to refer to under

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

This code is written according to the pseudo code of the software designer tutorial;
The most troublesome is not to change the pseudo-code to PHP, but the array subscript starting from 0, and the corresponding subscript judgment problem;
With a debug output piece written on

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$v _arr = Array (11,21,31,33,43,53,55,65); $w _arr = Array (1,11,21,23,33,43,45,55); $n = count ($w _arr); Test output Var_dump (BKNAP1 (110)); Var_dump (Bound (139,89,7,110)); function bound ($v, $w, $k, $W _total) { Global $v _arr, $w _arr, $n; $b = $v; $c = $w; Var_dump ($W _total); Var_dump ($n); Var_dump ($k); Var_dump ($v); Var_dump ($w); Die for ($i = $k +1; $i < $n; $i + +) { $c = $c + $w _arr[$i]; Var_dump ($W _total); Var_dump ($c); if ($c < $W _total) $b + = $v _arr[$i]; else{ Var_dump (($c-$W _total)/$w _arr[$i]) * $v _arr[$i]); $b = $b + (n ($c-$W _total)/$w _arr[$i]) * $v _arr[$i]; return $b; } } /*var_dump ('------bound head '); Var_dump ($K); Var_dump ($b); Var_dump ('------bound end '); */ return $b; } function Bknap1 ($W _total) { Global $v _arr, $w _arr, $n; $CW = $CP = 0; $k = 0; $fp =-1; while (true) { while ($k < $n && $CW + $w _arr[$k]<= $W _total) { $CW + = $w _arr[$k]; $CP + = $v _arr[$k]; $Y _arr[$k] = 1; $k +=1; } Var_dump ($CW), Var_dump ($CP), Var_dump ($Y _arr), Var_dump ($k); Var_dump ($n); if ($k = = $n) { $fp = $CP; $FW = $CW; $k = $n-1; $X _arr = $Y _arr; Bound ($CP, $CW, $k, $W _total); Var_dump (Bound ($CP, $CW, $k, $W _total), $fp, $k);d ie; Var_dump ($FP), Var_dump ($FW), Var_dump ($Y _arr), Var_dump ($k); Var_dump ($n); }else{ $Y _arr[$k] = 0; } Var_dump ($Y _arr); Var_dump ($k); Var_dump ($n);//die; Var_dump (Bound ($CP, $CW, $k, $W _total), $fp);d ie; while (Bound ($CP, $CW, $k, $W _total) <= $fp) { while ($k >=0 && $Y _arr[$k]!=1) { $k-= 1; } if ($k <0) { return $X _arr; } Var_dump ($K); $Y _arr[$k] = 0; $CW-= $w _arr[$k]; $CP-= $v _arr[$k]; } $k + = 1; } } ?>

I hope this article is helpful to everyone's PHP programming.

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