贪心算法01背包问题代码

01背包问题是一个经典的动态规划问题，不过也可以使用贪心算法来解决。贪心算法的思想是每次选择当前最优的解，从而得到全局最优解。对于01背包问题，可以按照物品的单位重量价值进行排序，然后依次选择单位重量价值最高的物品放入背包中，直到背包装满或者所有物品都被选择完为止。

以下是Java实现贪心算法解决01背包问题的代码：

import java.util.Arrays;

public class KnapsackProblem {
    public static void main(String[] args) {
        int[] weights = {2, 3, 4, 5};
        int[] values = {3, 4, 5, 6};
        int capacity = 8;
        double maxValue = knapsack(weights, values, capacity);
        System.out.println("The maximum value of items that can be carried is: " + maxValue);    }

    public static double knapsack(int[] weights, int[] values, int capacity) {
        int n = weights.length;
        double[] unitValues = new double[n];
        for (int i = 0; i < n; i++) {
            unitValues[i] = (double) values[i] / weights[i];
        }
        Item[] items = new Item[n];
        for (int i = 0; i < n; i++) {
            items[i] = new Item(weights[i], values[i], unitValues[i]);
        }
        Arrays.sort(items);
        double maxValue = 0;
        for (int i = 0; i < n && capacity > 0; i++) {
            if (items[i].weight <= capacity) {
                maxValue += items[i].value;
                capacity -= items[i].weight;
            } else {
                maxValue += capacity * items[i].unitValue;
                capacity = 0;
            }
        }
        return maxValue;
    }

    static class Item implements Comparable<Item> {
        int weight;
        int value;
        double unitValue;

        public Item(int weight, int value, double unitValue) {
            this.weight = weight;
            this.value = value;
            this.unitValue = unitValue;
        }

        @Override
        public int compareTo(Item other) {
            return Double.compare(other.unitValue, this.unitValue);
        }
    }
}