Java 修改二进制搜索算法，使其即使在未排序的列表上也能工作。

修改二进制搜索算法，使其即使在未排序的列表上也能工作。最好在主菜单中创建一个新选项（案例6），以便保留原始的二进制搜索。新的二进制搜索方法应该具有与前一种方法非常相似的结构，除了一些逻辑变化

这是我的原始代码：

// *****************************************************************
// IntegerListB.java
//
// Defines an IntegerList class with methods to create, fill,
// sort, and search in a list of integers. (Version B - for use
// in the binary search lab exercise)
//
// *****************************************************************
public class IntegerListB
{
    int[] list; //values in the list
    // ------------------------------------
    // Creates a list of the given size
    // ------------------------------------
    public IntegerListB (int size)
    {
        list = new int[size];
    }
    // -------------------------------------------------------------
    // Fills the array with integers between 1 and 100, inclusive
    // -------------------------------------------------------------
    public void randomize()
    {
        for (int i=0; i<list.length; i++)
            list[i] = (int)(Math.random() * 100) + 1;
    }
    // ----------------------------------------
    // Prints array elements with indices
    // ----------------------------------------
    public void print()
    {
        for (int i=0; i<list.length; i++)
            System.out.println(i + ":\t" + list[i]);
    }
    // ------------------------------------------------------------------
    // Returns the index of the first occurrence of target in the list.
    // Returns -1 if target does not appear in the list.
    // ------------------------------------------------------------------
    public int linearSearch(int target)
    {
        int location = -1;
        for (int i=0; i<list.length && location == -1; i++)
            if (list[i] == target)
                location = i;
        return location;
    }
    //-----------------------------------------------------------------
    //Returns the index of an occurrence of target in the list, -1
    //if target does not appear in the list.
    //-----------------------------------------------------------------
    public int binarySearchRec(int target)
    {
        return binarySearchR (target, 0, list.length-1);
    }
    //-----------------------------------------------------------------
    //Recursive implementation of the binary search algorithm.
    //If the list is sorted the index of an occurrence of the
    //target is returned (or -1 if the target is not in the list).
    //-----------------------------------------------------------------
    private int binarySearchR (int target, int lo, int hi)
    {
        int index;
        if ( hi < lo) // fill in the "not found" condition
            index = -1;
        else
        {
            int mid = (lo + hi)/2;
            if ( list[mid] == target) // found it!
                index = mid;
            else if (target < list[mid])
                // fill in the recursive call to search the first half
                // of the list
                index = binarySearchR(target, lo, mid-1);
            else
                // search the last half of the list
                index = binarySearchR(target, mid+1, hi);
        }
        return index;
    }

    //------------------------------------------------------------------
    //Sorts the list into ascending order using the selection sort algorithm.
    //------------------------------------------------------------------
    public void selectionSort()
    {
        int minIndex;
        for (int i=0; i < list.length-1; i++)
        {
            //find smallest element in list starting at location i
            minIndex = i;
            for (int j = i+1; j < list.length; j++)
                if (list[j] < list[minIndex])
                    minIndex = j;
            //swap list[i] with smallest element
            int temp = list[i];
            list[i] = list[minIndex];
            list[minIndex] = temp;
        }
    }

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二进制搜索需要按定义对元素进行排序

在计算机科学中，二进制搜索或半间隔搜索算法在按键值排序的数组中查找指定输入值（搜索“键”）的位置

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二进制搜索无法在未排序的列表上运行。这是先决条件之一。这可能要求深度优先搜索。如果有人发现了这个问题，他们应该得到一个特别的奖励！这是老师要求的，你已经有了一个叫做

selectionSort

的方法。我强烈怀疑您希望“选项6”首先使用该方法对列表进行排序，然后将其传递给已经存在的二进制搜索。

// ***************************************************************
// IntegerListBTest.java
//
// Provides a menu-driven tester for the IntegerList class.
// (Version B - for use with the binary search lab exerice)
//
// ***************************************************************
import java.util.Scanner;
public class IntegerListBTest
{
    static IntegerListB list = new IntegerListB (10);
    static Scanner scan = new Scanner(System.in);
    // ----------------------------------------------------------------
    // Create a list, then repeatedly print the menu and do what the
    // user asks until they quit.
    // ----------------------------------------------------------------
    public static void main(String[] args)
    {
        printMenu();
        int choice = scan.nextInt();
        while (choice != 0)
        {
            dispatch(choice);
            printMenu();
            choice = scan.nextInt();
        }
    }
    // ---------------------------------------------------
    // Does what the menu item calls for.
    // ---------------------------------------------------
    public static void dispatch(int choice)
    {
        int loc;
        switch(choice)
        {
        case 0:
            System.out.println("Bye!");
            break;
        case 1:
            System.out.println("How big should the list be?");
            int size = scan.nextInt();
            list = new IntegerListB(size);
            list.randomize();
            break;
        case 2:
            list.selectionSort();
            //invoke the sorting method in the IntegerListB class
            break;
        case 3:
            System.out.print("Enter the value to look for: ");
            loc = list.linearSearch(scan.nextInt());
            if (loc != -1)
                System.out.println("Found at location " + loc);
            else
                System.out.println("Not in list");
            break;
        case 4:
            System.out.print("Enter the value to look for: ");
            loc = list.binarySearchRec(scan.nextInt());
            if (loc != -1)
                System.out.println("Found at location " + loc);
            else
                System.out.println("Not in list");
            break;
        case 5:
            list.print();
            break;      
        default:
            System.out.println("Sorry, invalid choice");
        }
    }
    // ----------------------------
    // Prints the user's choices.
    // ----------------------------
    public static void printMenu()
    {
        System.out.println("\n Menu ");
        System.out.println(" ====");
        System.out.println("0: Quit");
        System.out.println("1: Create new list elements (** do this first!! **)");
        System.out.println("2: Sort the list using selection sort");
        System.out.println("3: Find an element in the list using linear search");
        System.out.println("4: Find an element in the list using binary search");
        System.out.println("5: Print the list");
        System.out.println("6: Find an element in the unsorted list using binary search");
        System.out.print("\nEnter your choice: ");  
    }
}