Question

我正在尝试确定对线性和二进制搜索技术进行了多少次比较。谁能告诉我如何打印出每个案例中循环发生的次数？例如，要在第一个数组中找到5，循环只发生一次。

       public static void main(String[] args) {
    // TODO code application logic here
    int[] values  = {5, 8, 6, 2, 1, 7, 9, 3, 0, 4, 20, 50, 11, 22, 32, 120};
    int[] valuesSorted  = {1, 2, 3, 4, 5, 8, 16, 32, 51, 57, 59, 83, 90, 104};
    DisplayArray(values);
    DisplayArray(valuesSorted);

    int index;
    index = IndexOf(1, values);
    System.out.println("1 is at values location " + index);
    index = IndexOf(120, values);

    System.out.println("120 is at values location " + index);

    index = BinaryIndexOf(104, valuesSorted);
    System.out.println("104 is at values Sorted location " + index);

    index = BinaryIndexOf(90, valuesSorted);
    System.out.println("90 is at values Sorted location " + index);       

}


public static int IndexOf(int value, int[] array)
{

    for (int i=0; i < array.length; i++)
    {

        if(array[i] == value)
            return i;

    }

    return -1;


}
public static int BinaryIndexOf(int value, int [] array)
{
    int start = 0;
    int end = array.length -1;
    int middle;

    while (end >= start)
    {
        middle = (start + end ) /2;
        if (array[middle]== value)
            return middle;
        if (array[middle]< value)
            start = middle + 1;
        else 
            end = middle - 1;
    }
    return -1;

}

public static void DisplayArray(int[] array)
{
    for (int a : array)
    {
        System.out.print(a + " ");
    }
    System.out.println();
}

}

Answer 1

对于线性搜索，您可以执行以下操作：

public static int IndexOf(int value, int[] array)
{
    for (int i=0; i < array.length; i++)
    {

        if(array[i] == value)
        {            
            System.out.println("Linear search: Number of comparisons = " + (i + 1));
            return i;
        }
    }

    return -1;
}

对于二进制搜索，请执行以下操作：

public static int BinaryIndexOf(int value, int [] array)
{
    int start = 0;
    int end = array.length -1;
    int middle;
    int loopCount = 0;
    while (end >= start)
    {
        loopCount++;
        middle = (start + end ) /2;
        if (array[middle]== value)
        {
            System.out.println("Binary search: Number of times looped = " + loopCount); 
            return middle;
        }
        if (array[middle]< value)
            start = middle + 1;
        else 
            end = middle - 1;
    }
    System.out.println("Binary search: Number of times looped = " + loopCount);
    return -1;

}

Answer 2

一种简单的方法是在类中创建一个计数器变量，并根据需要对其进行操作，如下所示：

private static int _loopCounter;

public static void main(String[] args) {
    // TODO code application logic here
    int[] values  = {5, 8, 6, 2, 1, 7, 9, 3, 0, 4, 20, 50, 11, 22, 32, 120};
    int[] valuesSorted  = {1, 2, 3, 4, 5, 8, 16, 32, 51, 57, 59, 83, 90, 104};
    DisplayArray(values);
    DisplayArray(valuesSorted);

    _loopCounter = 0;
    int index;
    index = IndexOf(1, values);
    System.out.println("1 is at values location " + index);
    System.out.println(_loopCounter + " comparisons were made.")

    _loopCounter = 0;
    index = IndexOf(120, values);
    System.out.println("120 is at values location " + index);
    System.out.println(_loopCounter + " comparisons were made.")

    _loopCounter = 0;
    index = BinaryIndexOf(104, valuesSorted);
    System.out.println("104 is at values Sorted location " + index);
    System.out.println(_loopCounter + " comparisons were made.")

    _loopCounter = 0;
    index = BinaryIndexOf(90, valuesSorted);
    System.out.println("90 is at values Sorted location " + index);
    System.out.println(_loopCounter + " comparisons were made.")       
}


public static int IndexOf(int value, int[] array)
{
    for (int i=0; i < array.length; i++)
    {
        _loopCounter++;
        if(array[i] == value)
            return i;
    }
    return -1;
}
    public static int BinaryIndexOf(int value, int [] array)
    {
    int start = 0;
    int end = array.length -1;
    int middle;

    while (end >= start)
    {
        _loopCounter++;
        middle = (start + end ) /2;
        if (array[middle]== value)
            return middle;
        if (array[middle]< value)
            start = middle + 1;
        else 
            end = middle - 1;
    }
    return -1;
}

public static void DisplayArray(int[] array)
{  
    for (int a : array)
    {
        System.out.print(a + " ");
    }
    System.out.println();
}

我没有测试这段代码，但我敢打赌你可以根据自己的需要修改它。

如何打印循环发生的次数？

2 个答案: