Example analysis of PHP backtracking to solve the 0-1 knapsack problem

This article mainly introduces the PHP backtracking method to solve the problem of 0-1 backpacks. The example analyzes the php backtracking method to solve the problem of backpack, which has some reference value, for more information about PHP backtracking, see the following example. Share it with you for your reference. The specific analysis is as follows:

This code is written according to the pseudocode in the software designer tutorial;
The most troublesome thing is not to change the pseudo code to php, but to judge the array subscript starting from 0 and the corresponding subscript;
Write it with debugging output

<? Php $ v_arr = array (, 33,); $ w_arr = array (, 43,); $ 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 (1-($ c-$ W_total) /$ w_arr [$ I]) * $ v_arr [$ I]); $ B = $ B + (1-($ 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_to Tal) {$ 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); die; // 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 ); die; 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 will help you with php programming.