背包问题(贪心java)

经过我不断测试发现确实不是最优解 

package TX;


import java.util.Arrays;

public class GreedyPackage {
    public void greedyPackage(int maxWeight,int[] weight,int[] val) {
        int n=weight.length;
        //性价比的数组
         double[] weightVal= new double[n];
         //按性价比存放i的数组
        int[] index=new int[n];
        for (int i = 0; i <n ; i++) {
            weightVal[i]=val[i]/weight[i];
            index[i]=i;//开始顺序
        }
        //按性价比进行排序 用降序排列
        for (int i = 0; i <n-1 ; i++) {
            for (int j = i+1; j <n ; j++) {
                if (weightVal[i]<weightVal[j]){
                    double temp=weightVal[i];
                    weightVal[i]=weightVal[j];
                    weightVal[j]=temp;
                    //交换下标
                    int ind=index[i];
                    index[i]=index[j];
                    index[j]=ind;
                }
            }
        }
        int[] x=new int[n];
        int maxval=0;
        for (int i = 0; i <n ; i++) {
            if (maxWeight>weight[index[i]]){
                x[i]=1;
                System.out.println(weight[index[i]]+"被放入背包");
                maxWeight-=weight[index[i]];
                maxval+=val[index[i]];
            }
        }
        System.out.println(maxval);
            System.out.print(Arrays.toString(x));
    }
    public  static void main(String[] args){
        GreedyPackage a=new GreedyPackage();
        int [] wight={35,30,60,50,40,10,25};
        int[] val={10,40,30,50,35,40,30};
        a.greedyPackage(150,wight,val);
    }
}

 

对于背包问题贪心算法,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,直到背包装满或者没有可选的物品为止。这个算法可以通过以下Java代码实现: ```java public class KnapsackGreedy { public static int maxValue(int[] values, int[] weights, int max){ if(values == null || values.length == 0){ return 0; } if(weights == null || weights.length == 0){ return 0; } if(max <= 0){ return 0; } int n = values.length; double[] valuePerWeight = new double[n]; for(int i=0; i<n; i++){ valuePerWeight[i] = (double) values[i] / weights[i]; } int[] sortedIndex = new int[n]; for(int i=0; i<n; i++){ sortedIndex[i] = i; } Arrays.sort(sortedIndex, (a, b) -> Double.compare(valuePerWeight[b], valuePerWeight[a])); int maxValue = 0; int currentWeight = 0; for(int i=0; i<n; i++){ int index = sortedIndex[i]; if(currentWeight + weights[index] <= max){ maxValue += values[index]; currentWeight += weights[index]; } } return maxValue; } public static void main(String[] args) { int[] values={6,3,5,4,6}; int[] weights={2,2,6,5,4}; int max = 10; System.out.println(maxValue(values,weights,max)); } } ``` 以上是一个简单的贪心算法实现,它通过计算每个物品的单位重量价值,并按照降序对物品进行排序。然后依次选择单位重量价值最高的物品放入背包中,直到背包装满或者没有可选的物品为止。该算法的时间复杂度为O(nlogn),其中n为物品的数量。<span class="em">1</span><span class="em">2</span><span class="em">3</span> #### 引用[.reference_title] - *1* [背包问题Java实现)——贪心算法](https://blog.youkuaiyun.com/qq_40956679/article/details/83684383)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v93^chatsearchT3_1"}}] [.reference_item style="max-width: 50%"] - *2* *3* [java语言贪心算法背包问题](https://blog.youkuaiyun.com/ityw520/article/details/121514232)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v93^chatsearchT3_1"}}] [.reference_item style="max-width: 50%"] [ .reference_list ]
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