Question

我有一个LinkedList的ADT测试代码，它实现了NumList.java接口，并在NumLinkedList.java中实现，并在NumSet.java中使用它。

我正在努力使我的NumSet具有可以从双数组输入创建集合的方法，并使用intercept / union和print方法来使用和打印数据。

但我的测试代码显示我的测试NumSet值为空，即testProof和testProof2。

所以现在我的testProof返回一个空变量，这意味着什么都没有保存到它。

static public NumSet intersect(NumSet S1, NumSet S2) //check 2nd for and if//
{
    NumSet intersectAnswer = new NumSet();

    for (int i = 0; i < S1.set.size()-1; i++)
    {
        for(int j = 0; j < S2.set.size()-1; j++)
        {
            double FUZZ = 0.0001;
            if (Math.abs(S1.set.lookup(i) - S2.set.lookup(j)) < FUZZ) // double values, this is more precise than ==.
                {
                    intersectAnswer.set.insert(1, S1.set.lookup(i));
                }
        }
    }

    return intersectAnswer;

}

是testProof的方法，以下是定义testProof的地方。

public static void main(String[] args)
{
    double[] a = {1.3,2,3,4,101.9};
    double[] b = {3,7,13,901,-29.1,0.05};

    NumArrayList test;
    test = new NumArrayList();
    test.printTest(); //runs test code in NumList


    //ok below is running. what is wrong with intersect?
    NumSet test2;
    test2 = new NumSet(a);
    NumSet test4;
    test4 = new NumSet(b);
    NumSet testProof;
    NumSet testProof2;

    test2.print(); //print out test 2
    System.out.println();
    test4.print();
    System.out.println();
    testProof = intersect(test2,test4);

我已初始化为

public class NumSet
{
private NumList set;

    public NumSet(double[] sth)
    {
        //moves elements of sth into set.
        set = new NumLinkedList();
        for(int i = 0; i < sth.length; i++)
        {
            set.insert(0,sth[i]);
        }
        set.removeDuplicates();
    }

    public NumSet()
    {
        set = new NumLinkedList();
    }

int numSet = 0;

我的拦截，联合和打印如下：

public NumSet intersect(NumSet S1, NumSet S2) //check 2nd for and if//
{
    NumSet intersectAnswer = new NumSet();

    for (int i = 0; i < S1.set.size()-1; i++)
    {
        for(int j = 0; j < S2.set.size()-1; j++)
        {
            if (S1.set.lookup(i) == S2.set.lookup(j))
                {
                intersectAnswer.set.insert(0, S1.set.lookup(i));
                }
        }
    }

    // intersectAnswer.set.removeDuplicates();  unnecessary, sets are already removed of duplicates
    return intersectAnswer;

}

public NumSet union(NumSet S1, NumSet S2)
{   //check logic.
    NumSet unionAnswer = new NumSet();

    for (int i = 1; i < S1.set.size()+1; i++)
    {
        unionAnswer.set.insert(1, S1.set.lookup(i));
    }

    for (int i = 1; i < S2.set.size()+1; i++)
    {
        unionAnswer.set.insert(1, S2.set.lookup(i)); 
    }
    unionAnswer.set.removeDuplicates();
    return unionAnswer;
}

public void print() 
{
    for (int i = 0; i < set.size()-1; i++)
    {
        System.out.print(set.lookup(i) + ",");

    }
    System.out.print(set.lookup(set.size()-1));
}

查询和大小是从我的NumLinkedList.java引用的，如下所示

public int size() // measure size of list by counting counter++;
{


    return nItem; 
}


public double lookup(int i) 
{
    if( i <0 || i >= size()) //cannot lookup nonexistant object
    {
        System.out.println("out of bounds " + i + " < 0 or > " + size() );
        //how do I break out of this loop?
        System.out.println("just returning 0 for the sake of the program");

        return 0;
    }

    if(i == 0)
    {
        return head.value;
    }

    double answer = 0;
    Node currNode = head;
    for(int j = 0; j < i+1; j++) //move to ith node and save value
    {
        answer = currNode.value;    
        currNode = currNode.next;   
    }

    return answer;
}

最后我的测试代码如下，其中testProof和testProof2是。

public static void main(String[] args)
{
    double[] a = {1.3,2,3,4,101.9};
    double[] b = {3,7,13,901,-29.1,0.05};

    NumArrayList test;
    test = new NumArrayList();
    test.printTest(); //runs test code in NumList


    //ok below is running. what is wrong with intersect?
    NumSet test2;
    test2 = new NumSet(a);
    NumSet test4;
    test4 = new NumSet(b);
    NumSet testProof;
    NumSet testProof2;

    test2.print();
    System.out.println();
    testProof = test2.intersect(test2, test4);
    System.out.println("tried intersect");
    testProof.print(); 
    System.out.println();
    System.out.println("tried test.print()");
    testProof2 = test2.union(test2,test4);
    System.out.println("tried union");
    testProof2.print(); 
    System.out.println();
    System.out.println("NumSet ran fully.");

Answer 1

我建议您在调试时使用整数值而不是 double values 来实现NumSet类，因为比较两个double值会给代码增加一些不必要的复杂性在这个调试阶段。

您可能希望查看 removeDuplicates（）方法，我认为这可能会解决您的问题。不幸的是，我没有在你发布的代码中看到它。

实际上， intersect（）方法中的这部分代码注定要从一开始就失败，

if (S1.set.lookup(i) == S2.set.lookup(j))

由于你使用了双精度数，==是比较两个不同值的非常不精确的方法，更好的方法是允许一定量的精度误差，即

double final FUZZ = 0.0001
if (Math.abs(S1.set.lookup(i) - S2.set.lookup(j)) < FUZZ )
    //...

ADT链接列表交集设置错误

1 个答案: