75 lines
2.8 KiB
Java
75 lines
2.8 KiB
Java
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/*
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This is java program to implement 0/1 Knapsack problem. The knapsack problem or rucksack problem is a problem in combinatorial optimization: Given a set of items, each with a mass and a value, determine the number of each item to include in a collection so that the total weight is less than or equal to a given limit and the total value is as large as possible. It derives its name from the problem faced by someone who is constrained by a fixed-size knapsack and must fill it with the most valuable items.
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*/
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//This is a sample program to implement a 0/1 knapsack algorithm
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import java.util.Scanner;
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public class Zero_One_Knapsack
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{
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public void solve(int[] wt, int[] val, int W, int N)
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{
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int NEGATIVE_INFINITY = Integer.MIN_VALUE;
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int[][] m = new int[N + 1][W + 1];
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int[][] sol = new int[N + 1][W + 1];
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for (int i = 1; i <= N; i++)
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{
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for (int j = 0; j <= W; j++)
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{
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int m1 = m[i - 1][j];
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int m2 = NEGATIVE_INFINITY;
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if (j >= wt[i])
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m2 = m[i - 1][j - wt[i]] + val[i];
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m[i][j] = Math.max(m1, m2);
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sol[i][j] = m2 > m1 ? 1 : 0;
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}
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}
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int[] selected = new int[N + 1];
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for (int n = N, w = W; n > 0; n--)
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{
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if (sol[n][w] != 0)
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{
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selected[n] = 1;
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w = w - wt[n];
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}
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else
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selected[n] = 0;
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}
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System.out.print("\nItems with weight ");
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for (int i = 1; i < N + 1; i++)
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if (selected[i] == 1)
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System.out.print(val[i] +" ");
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System.out.println("are selected by knapsack algorithm.");
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}
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public static void main (String[] args)
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{
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Scanner scan = new Scanner(System.in);
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Zero_One_Knapsack ks = new Zero_One_Knapsack();
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System.out.println("Enter number of elements ");
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int n = scan.nextInt();
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int[] wt = new int[n + 1];
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int[] val = new int[n + 1];
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System.out.println("Enter weight for "+ n +" elements");
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for (int i = 1; i <= n; i++)
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wt[i] = scan.nextInt();
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System.out.println("Enter value for "+ n +" elements");
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for (int i = 1; i <= n; i++)
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val[i] = scan.nextInt();
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System.out.println("Enter knapsack weight ");
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int W = scan.nextInt();
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ks.solve(wt, val, W, n);
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scan.close();
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}
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}
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/*
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Enter number of elements
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5
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Enter weight for 5 elements
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01 56 42 78 12
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Enter value for 5 elements
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50 30 20 10 50
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Enter knapsack weight
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150
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Items with weight 50 30 20 50 are selected by knapsack algorithm.
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