Case study of PHP greedy algorithm for solving the 0-1 knapsack problem

Case study of PHP greedy algorithm for solving the 0-1 knapsack problem

This article mainly introduces the PHP greedy algorithm to solve the 0-1 knapsack problem. The example analyzes the principles of the greedy algorithm and the implementation skills of the knapsack problem. For more information, see

 

 

This article describes how to solve the 0-1 knapsack problem by using the PHP greedy algorithm. Share it with you for your reference. The specific analysis is as follows:

The greedy algorithm solves the problem of 0-1 backpacks. The global optimal solution is obtained through the local optimal solution! This solution is more flexible than dynamic planning!

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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 result Function display ($ x) { $ Len = count ($ x ); Foreach ($ x as $ val ){ Echo $ val-> weight, '', $ val-> price; Echo '<br> '; } } // 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-incrementing order Display ($ x); // display Echo '0-1 the optimal solution of the backpack is :'; Echo tanxin ($ x );

I hope this article will help you with php programming.